KIEV (CNN) -- A contingent of U.S. Army paratroopers arrived in Poland on Wednesday, the first of what will be a "persistent presence" of U.S. troops as the crisis in nearby Ukraine continues to unfold.
The company-sized contingent will conduct training exercises with Polish counterparts and is visiting at the request of Poland.
The joint exercises are a symbol of force as the conflict in Ukraine between pro-government and pro-Russian factions continues unabated. The United States and Russia accuse each other of fomenting unrest in Ukraine.
The U.S. troops stood in formation at an airfield next to Polish troops as military leaders from both countries addressed them, reiterating the alliance between their nations.
"Poland has been there for the United States, and today, as the transatlantic community confronts Russia's unacceptable aggression against Poland's neighbor, Ukraine, a sovereign and independent state, we have a solemn obligation in the framework of NATO to reassure Poland of our security guarantee," said Stephen Mull, the U.S. ambassador to Poland.
The United States will maintain a presence in Poland at least through the end of the year, he said.
Russia has deployed what NATO estimates to be 40,000 troops near its border with Ukraine, something that has made other countries like Poland nervous.
The military exercises in the Polish city of Swidwin are "a result of what's going on in Ukraine," Pentagon spokesman Rear Adm. John Kirby said Tuesday. "What we're after here is persistent presence, a persistent rotational presence."
Four companies of paratroopers based in Italy will be sent to Poland, Lithuania, Latvia and Estonia over the next few months for military exercises, he said.
Addressing the assembled troops from the U.S. and Poland on Wednesday, U.S. Army Maj. Gen. Richard C. Longo said the joint exercises are a manifestation of the strong commitment the two countries have to each other.
"Despite the uncertainty of the world and this region, I am certain of one thing about the United States Army in Europe: We have the capacity, we have the commitment, we have the will to fulfill our NATO obligations," he said.
Anti-terror measures in Ukraine
Pro-Russian militants will be targeted in four key cities in Ukraine's restive east, Ukraine's deputy prime minister said Wednesday.
"The active phase of the anti-terrorist operation continues," Vitaliy Yarema was quoted as saying by state-run news agency Ukrinform.
Militants in the four cities -- Kramatorsk, Slaviansk, Donetsk and Luhansk -- have seized government buildings and show no signs of giving them up despite an international deal agreed to last week in Geneva, Switzerland.
On Tuesday, acting President Oleksandr Turchynov also urged a renewal of anti-terror measures after a truce called during the Easter holiday, citing the discovery of two tortured bodies near Slaviansk -- one of them a pro-Kiev politician from his own party.
A statement from a pro-Russian leader in Slaviansk, de facto Mayor Vyacheslav Ponomaryov, rejected Turchynov's claim and blamed the deaths on far-right Ukrainian nationalist extremists.
Under the Geneva deal, illegal militia groups were to disarm and vacate occupied buildings, with an amnesty promised in return.
But the pact, aimed at easing tensions in eastern Ukraine, appears to be faltering six days on, with Kiev and Moscow accusing each other of failing to live up to its commitments.
Meanwhile, the war of words continues.
Lavrov: Americans 'running the show'
Ukrainian and U.S. officials say they think Russian special forces are in the region and are behind efforts to seize government buildings and generally promote unrest -- a claim Moscow denies.
On the contrary, Russian Foreign Minister Sergey Lavrov told Russia's state-run RT news channel Wednesday that the United States is calling the shots in Ukraine.
As proof of this, he pointed to the timing of the Ukrainian government's relaunch of its security operation, just after a two-day visit to Ukraine by U.S. Vice President Joe Biden.
"Now that Joe Biden visited Kiev, this counterterrorist operation was declared in the active phase again," he told RT.
"I don't have any reasons not to believe that the Americans are running the show in a very close way."
Lavrov also said that Russia would "certainly respond" if its interests were attacked in Ukraine.
"If our interests, our legitimate interests, the interests of Russians have been attacked directly, like they were in South Ossetia for example, I do not see any other way but to respond in accordance with international law," he told RT.
"Russian citizens being attacked is an attack against the Russian Federation."
Lavrov added that U.S. involvement in Ukraine "is just one manifestation of the American unwillingness to yield in the geopolitical fight. Americans are not ready to admit that they cannot run the show in each and every part of the globe from Washington alone."
Ukraine to request IMF loan
Prime Minister Arseniy Yatsenyuk said Wednesday that the Cabinet has approved a formal request to the International Monetary Fund for a loan, which would help stabilize the economic situation in Ukraine. Yatsenyuk said he hoped to receive the answer by the end of the month.
Ukraine's dire economic situation has added to the pressures on the interim government ahead of national elections due on May 25.
Speaking in Kiev on Tuesday, Biden said he expects an IMF package for Ukraine to be finalized imminently.
He also promised U.S. support for Ukraine and stressed that the United States won't recognize Russia's annexation of Crimea.
The United States also promised Tuesday an additional $50 million to support political and economic reform in Ukraine, including just over $11 million to help run the elections next month.
In another sign of international support for the government in Kiev, the Vatican said Pope Francis would meet Yatsenyuk on Saturday in Rome. The prime minister will meet afterward with the Vatican Secretary of State, Monsignor Pietro Parolin.
American journalist held
An American journalist working for Vice News is being held by pro-Russian separatists in Slaviansk, Vice News said in a statement posted on its website Tuesday.
The international channel said it is in contact with the U.S. State Department and other appropriate government authorities to secure the release of Simon Ostrovsky.
State Department spokeswoman Jen Psaki said Wednesday, "We are deeply concerned about the reports of a kidnapping of a U.S. citizen journalist ... reportedly at the hands of pro-Russian separatists."
Such hostage takings violate the terms of the Geneva agreement, she said.
"We call on Russia to use its influence with these groups to secure the immediate and safe release of all hostages in eastern Ukraine," Psaki added.
Torture, detention allegations
Ukraine's Interior Ministry said Wednesday that Vladimir Rybak, the politician found dead near Slaviansk, died as a result of injuries from torture and drowning.
His body was discovered Saturday, two days after witnesses said he was kidnapped by men in military clothing and balaclavas, following an altercation with protesters at the local city hall, the ministry said.
According to investigators, representatives of a separatist group involved in seizing the Security Service office in Slaviansk were also involved in torturing him, the ministry said.
An adviser to the interior minister, Stanislav Rechinsky, also pointed the finger at pro-Russian separatists Wednesday.
"We already know the location where the torture took place and where an unknown number of kidnapped residents of Slaviansk and journalists are held captive," he said at a news conference.
"We have eyewitnesses who testified about hearing the so-called little green men bragging about the murders. We have another eyewitness who saw these men alive in the torture cells and who was able to escape."
The term "little green men" has become widely used for the unidentified armed men who have appeared in eastern Ukraine in recent days. Russia has denied they are Russian military forces in uniforms that don't bear insignia.
™ & © 2014 Cable News Network, Inc., a Time Warner Company. All rights reserved.