A Russian soldier serving in the Caucasus has killed at least five of his fellow border guards in a shooting spree - reportedly after eating hallucinogenic mushrooms.

At least three others were injured in the incident on Russia's southern border with Georgia.

The soldier fired his Kalashnikov assault rifle at a tent where his comrades were resting while deployed on patrol, the Associated Press news agency reported.

Some were killed on the spot, others died later of their wounds in hospital, it said.

Preliminary investigations suggested that the soldier - named as Denis Solovyev - was in a state of narcotic intoxication, Yuri Kolodkin, a spokesman with the Emergency Situations Ministry was quoted as saying.

Witnesses said he had eaten hallucinogenic mushrooms not long before the incident, at the Ptysh border guard post.

Collecting mushrooms - though not usually for hallucinogenic properties - is a Russian passion

Correspondents say tales of substance abuse are common in the Russian army, which suffers from poor discipline, low morale and under funding and is plagued by brutality, shootings and desertions.

In a similar incident in August, two border guards killed eight fellow-servicemen who were asleep while on patrol in the same part of the country, saying they did it to avenge bullying.

In September, more than 50 soldiers abandoned their unit and marched nearly 60 kilometres (35 miles) to the city of Volgograd to protest against beatings by their officers.