SIMFEROPOL (REUTERS) - Prime Minister Dmitry Medvedev flaunted Russia's grip on Crimea by flying to the region and holding a government meeting there on Monday, angering Ukraine and defying Western demands to hand the peninsula back to Kiev.

But in a gesture that could ease tension in the worst East-West stand-off since the Cold War, Russia pulled some troops back from near Ukraine's eastern frontier - a move which the United States said would be a positive sign if it is confirmed as a withdrawal.

At the Kadamovsky training ground, a Reuters reporter saw hundreds of troops pile into over 40 armoured personnel carriers and a long line of military trucks. The convoy then headed off from the area, which lies in the Rostov border region.

President Vladimir Putin told German Chancellor Angela Merkel that he had ordered a partial drawdown in the region, Merkel's spokesman said.

However, Medvedev's visit taunted Western leaders by underlining their inability to force Putin to relinquish Crimea, seized after the overthrow of Russian-backed Ukrainian President Viktor Yanukovych and formally annexed on March 21.

Accompanying Medvedev, outspoken Deputy Prime Minister Dmitry Rogozin - who has been targeted by Western sanctions - left no doubt about the symbolism of the trip, saying on Twitter: "Crimea is ours. Basta!" The Ukrainian government denounced the visit as a "crude violation" of the rules of diplomacy, a few hours after the latest round of crisis talks between Russia and the United States ended inconclusively.

Western countries have expressed concern about a Russian troop buildup on the Ukraine border.

However, the Russian Defence Ministry said a battalion from the central military district's 15th motorised infantry brigade was pulling back to its home base of Samara on the Volga River after what it called month-long exercises.

In Washington, the White House reacted cautiously to the troop movements. "We've seen the reports and if they are true and if - more importantly - they represent further withdrawals, that would be a positive sign," said spokesman Jay Carney. "It is certainly something that we have explicitly called for."