An interior ministry source told the official QNA news agency that Yandarbiyev, who was residing in Qatar "temporarily," was killed and his 13-year-old son wounded when a blast targeted their car as they returned from weekly prayers at a Doha mosque.

Investigation

The source said authorities had launched an investigation into the fatal attack. Qatar's public security chief Mubarak Hassan al-Nasr later told the Doha-based Al-Jazeera news channel the evidence was still being collected and finger-pointing would be premature.

A source at Al-Hamad hospital, where Yandarbiyev succumbed to serious injuries sustained in the explosion, told AFP that his son, Daoud, was in stable condition.

Officials did not give details about the nature of the blast shortly after the noon Muslim prayers.

Bomb may have been planted

Witnesses said it occurred at a crossing in the Al-Dafna residential area, some 300 metres from the mosque. They said they saw no explosive device being hurled at Yandarbiyev's white Land Cruiser, suggesting a time bomb might have been planted inside the vehicle or that an explosive was detonated by remote control.

The car was burned by the explosion.

Russia had demanded Yandarbiyev's extradition, but its SVR foreign intelligence service denied Chechen rebel accusations that it was involved in the death of the 51-year-old ex-leader of the war-torn republic, who had been living in Qatar for three years.

Qatari newspaper editor Abdul Latif al-Mahmud told Al-Jazeera he did not think Friday's assassination would prompt Doha to distance itself from what the television described as "hot issues," saying Qatar had played a positive political role on many fronts in the past few years.

Qatar tries to mediate regional disputes

Gas-rich Qatar, a close US ally which served as the US Central Command's operations base during last year's war on Iraq, has repeatedly tried to mediate in regional disputes, a policy which critics say is a size too big for the tiny Gulf state.

Doha has also often ruffled the feathers of Arab governments by hosting their most outspoken opponents.

Dissidents from Saudi Arabia and Bahrain have frequently been offered a platform on Al-Jazeera to lambaste their governments, sparking crises between Doha and its fellow Gulf states.

Qatar is also part-time home ? along with Syria ? to Khaled Mishaal, a prominent leader of the Palestinian Islamist group Hamas that opposes Yasser Arafat's policy of seeking a negotiated settlement with Israel.

A more recent beneficiary of Qatari hospitality has been Abbasi Madani, leader of Algeria's banned Islamic Salvation Front (FIS), who has been here since November, ostensibly to undergo medical treatment.

Hours after the blast that killed Yandarbiyev, and which the public security chief called an unprecedented event in Qatar, Doha issued a statement showing that the use of its good offices can pay off.

A foreign ministry official said the Polisario Front, a movement seeking independence for the Moroccan-occupied Western Sahara desert territory, had released 100 Moroccan prisoners of war following Qatari mediation.

Yandarbiyev was a leader of Chechnya's separatist movement and briefly headed the Caucasus republic toward the end of its first war with Moscow in 1996.

Russia accused Yandarbiyev of involvement in the seizure of more than 800 hostages by Chechen rebels at a theatre in Moscow in October 2002. A total of 130 hostages died, most of them during a police raid to secure their release, as did all 41 Chechen rebels.