A Russian soldier on Friday opened fire on troops at a Siberian military base, killing eight and injuring two, officials said, blaming the attack on a possible "nervous breakdown".
The incident took place at an army base in the Chita region in eastern Siberia during a change of guard.
"The serviceman who opened fire has been detained," the defence ministry said in a statement.
Russia's Investigative Committee, which probes major crimes, said the shooter was a conscript named Ramil Shamsutdinov and launched a murder case.
The base is located in the town of Gorny which is closed to all outsiders without a special permit and is managed by the Ministry of Defence directorate responsible for maintaining Russia's nuclear arsenal.
Officials claimed the incident was not work related.
"The actions of the serviceman could be the result of a nervous breakdown caused by personal circumstances not connected to his military duty," the defence ministry said, quoted by Russian news agencies.
The wounded were hospitalised, the ministry said.
Andrei Kurochkin, the deputy chairman of soldiers rights organisation Committee of Soldiers' Mothers, said that in general such cases of mass murder are the result of abuse and total desperation.
"Commanders just close their eyes to cases of systematic bullying," he told AFP.
Senior officers leave victims with no means of complaining by confiscating their phones and overseeing all conversations with relatives, he said.
"They say it's to protect state secrets, but in reality that's the last priority," he said.
When such cases are probed, "investigators come to the base and interview soldiers who have already been briefed on what to say," Kurochkin said.
State news agency TASS, quoting a source, said two of the victims were officers, while the rest were conscripts and contract servicemen.
TASS said the two wounded were in a serious condition and would probably be flown to Moscow for treatment.
A commission chaired by Deputy Defence Minister Andrei Kartapolov was on its way to the base.
A defence ministry spokesman declined to comment when reached by AFP.
Brutal hazing rituals were a major problem in the Russian army in the 1990s but this has significantly improved in recent years.
Military conscription is compulsory in Russia for all male citizens aged between 18 and 27.