At least 11 people were killed and 15 wounded on October 15 at a military training ground in the Belgorod region of Russia when two attackers opened fire on a group of volunteers, the Russian Defense Ministry said.

The ministry said two volunteer soldiers fired at other troops at the training ground, described as a Russian military firing range.

The ministry said in a statement that the shooting occurred as volunteers trained to fight in Ukraine. It called the incident a terrorist attack.

"During a firearms training session with individuals who voluntarily expressed a desire to participate in the special military operation (against Ukraine), the terrorists opened fire with small arms on the personnel of the unit," Russian media cited a Defense Ministry statement as saying.

It said the two volunteers who fired on the other soldiers were shot dead by return fire. It was unclear whether their deaths are included among the 11 confirmed dead. The two were nationals from a former Soviet republic, the ministry said, but did not give any other details.

The Moscow-based Baza news website reported that the shooting took place at about 10 a.m., but it only became known in the evening.

The motive for the attack is unclear.

Russian President Vladimir Putin announced a mobilization on September 21, sparking protests, attacks on recruitment offices, and the flight of huge numbers of men out of the country.

Putin said on October 14 that Russia should be finished calling up reservists in two weeks, promising to end the mobilization after the conscription of more than 200,000 men to fight in Ukraine.

With reporting by Reuters and AP