The last time Valeria Sokolova saw her husband, the 25-year-old paratrooper told her that he and his fellow soldiers were heading for military exercises in southern Russia, near the Ukrainian border.

"He was vague in a way that was very unusual, and it was hard for all of them to say goodbye," Sokolova told The Associated Press, recounting their conversation from earlier this month.

On Monday, 10 men from his division were captured in eastern Ukraine amid fighting between pro-Moscow separatists and Ukrainian troops. At least two others from the division were killed and an unspecified number were wounded.

Sokolova, the mother of a 6-year-old boy, does not know the fate of her husband, and she said Russian military officials have released no information about the servicemen. She fears for his safety.

Similar questions are being raised by families of other Russian servicemen about unexplained deaths and missing or captured soldiers who are said to be on military exercises. The answers could undermine public support for President Vladimir Putin and his policies in Ukraine.

The government has released little information about those killed while fighting with the rebels, a policy that some have compared to one used during the Soviet intervention in Afghanistan in the 1980s. This secrecy may become more difficult to maintain if the death toll grows.

Sokolova, who declined to identify her husband further because she worries it could have consequences for him, said she and other army wives converged on the local garrison to demand answers.

"Only through each other did we find out the number of killed, wounded," she told the AP by telephone from Kostroma, a city 210 miles north of Moscow.

Russian officials, including Putin, have said the captured paratroopers had gotten lost and wandered over the border by mistake.

The news added to the growing evidence that Russia, despite its denials, is sending troops and weapons to fight alongside the separatists.

On Thursday, Ukraine accused Russia of sending tanks, armored vehicles and troops onto its soil. NATO said at least 1,000 Russian troops are in Ukraine and released what it said were satellite photos of Russian artillery units moving in last week.

Rebel leader Alexander Zakharchenko said up to 4,000 Russians have fought on the separatist side since the conflict began in April, including soldiers, but he said they were on leave and fighting voluntarily.