Thousands of mourners converged on a cemetery in Russia's republic of Dagestan on Tuesday night for the burial of a top Muslim religious leader who was killed in a suicide bombing hours earlier, Russian news agencies said.

Said Afandi, a leader of Sufi Muslims in the region, and five of his followers were killed by a female suicide bomber in an attack at Afandi's home in the village of Chirkei, said Dagestan Interior Ministry spokesman, Vyachelav Gasanov.

There was no immediate claim of responsibility or identification of the bomber, but the attack could be linked to tensions between Sufis and the Wahhabi sect that is the core of the insurgency in the republic. Afandi was a frequent public critic of Wahhabism.

In July, a top Muslim cleric in the Volga River republic of Tatarstan was gunned down and the republic's chief mufti was wounded when a bomb ripped through his car. Both victims had been vocal critics of radical groups that advocate a strict and puritan version of Islam known as Salafism.

In a visit to Tatarstan on Tuesday, Russian President Vladimir Putin presented state awards to the wounded mufti, Ildus Faizov, and relatives of the slain cleric Valiullah Yakupov.

Putin called for interethnic harmony and said of extremists: "You cannot defeat a unified, multinational, strong Russian nation because on the side of truth and justice are millions of people who fear nothing, who cannot be intimidated and know the price of peace."

The killing of Afandi highlighted the violent tensions that persist in Dagestan, even as neighboring Chechnya has become relatively pacified and orderly after two wars in the last 20 years between separatists and Russian forces.

Clashes with militants and attacks on police occur almost daily in Dagestan.

The Interfax and RIA Novosti news agencies said witnesses reported tens of thousands of mourners came to Afandi's burial.

Also Tuesday in Dagestan, a border guard opened fire on colleagues at a barracks, killing seven before being shot to death himself, Gasanov said. There was no indication of motivation.