"Ten soldiers died and seven were injured," Dagestan's deputy prosecutor, Zaur Issayev, said. "All the dead were from the Russian interior ministry force."

The explosion occurred outside a public baths used by troops in Makhachkala, capital of Dagestan, which is next to Chechnya in the turbulent North Caucasus region.

Investigators told ITAR-TASS news agency that an estimated 10 kilograms (22 pounds) of explosive were used in the bomb. They said the device was probably set off by radio control -- a common tactic of militants.

The blast blew the windows from three light military trucks parked outside the baths and shredded their canvas coverings, an AFP correspondent at the scene said. The bath building was damaged and windows were broken in neighbouring buildings.

Police cordoned off the area.

Attacks on troops and police in Dagestan, which has a population of about 2.5 million people, nearly all of them Muslim, have grown steadily in number this year.

According to official figures, 30 officers have been killed this year and at least 40 injured in bombings and shootings around Dagestan, most of them in Makhachkala.