Polish Foreign Minister Radoslaw Sikorski on Friday described the fighting in neighboring Ukraine as a "war", as the West accused Moscow of direct involvement in the escalating conflict.

"If it looks like a war, sounds like a war and kills like a war, it is a war," Sikorski wrote on Twitter about the now four-month conflict between government troops and pro-Moscow rebels.

U.S. Army troops equipped with tanks will head to Eastern Europe soon to reassure NATO allies anxious over Russia's intervention in Ukraine, Pentagon officials said Thursday.

About 600 troops from the 1st Brigade, 1st Cavalry Division are due to deploy in October to Poland and the Baltic states for training exercises with alliance members, replacing paratroopers from the 173rd Airborne Brigade, said spokeswoman Lieutenant Colonel Vanessa Hillman.

Poland's prime minister said Wednesday there is evidence that regular units of the Russian army are operating in Ukraine, according to information from NATO and Polish intelligence.

"No one can take seriously talk of separatists in Ukraine at this point," Prime Minister Donald Tusk told parliament regarding the crisis in neighboring Ukraine.

NATO is preparing a rapid response to the Ukraine crisis that would allow it to deploy troops swiftly to reinforce eastern Europe and dissuade Russia from further destabilizing the region, the alliance chief Anders Fogh Rasmussen said on Wednesday.

Britain on Monday announced major joint manoeuvres in Poland in October, part of a string of NATO exercises in the region aimed at reassuring eastern Europe members jittery over a resurgent Russia.

"I can announce today exercise Black Eagle, which will be a significant Polish and UK armored exercise with over 350 British armored and other vehicles and some 1,350 British personnel," British Defense Secretary Michael Fallon said in Warsaw.

The Polish government has canceled plans for a year of cultural celebrations with Russia out of anger with Russian actions in Ukraine.

The Foreign Ministry said Thursday that it summoned the Russian ambassador to inform him of the decision.

Europe's top human rights court condemned Poland on Thursday for hosting secret CIA prisons on its territory, saying Warsaw knowingly abetted unlawful imprisonment and torture of Guantanamo-bound detainees.

Presidents from nine ex-communist NATO members met in Warsaw on Tuesday for talks on how to re-enforce the alliance's eastern frontier as if faces a resurgent Russia.

"The Russia-Ukraine conflict is Europe's most important security challenge since the end of the Cold War," Polish President Bronislaw Komorowski told reporters as the leaders met to forge their regional defense strategy ahead of a NATO summit in September.

At least 10 people were killed and more than 50 hurt on Saturday as a coach carrying Polish holidaymakers collided with another Polish minibus near the eastern German city of Dresden, police said.

The crash happened in the early hours of Saturday morning on the A4 motorway that links Poland and Germany, with police initially putting the death toll at nine killed and 43 injured.

Polish Prime Minister Donald Tusk is to face a second confidence vote in as many weeks as the country's opposition seeks to force his center-right government to resign over a high-profile bugging scandal.

The opposition conservative Law and Justice (PiS) party said on Tuesday it would put forward a motion in parliament calling on the government to step down.