MOSCOW (AP) _ A bomb exploded outside a central Moscow restaurant Thursday, killing a security agent in an attack authorities said was the work of a terrorist ring training female suicide bombers for national strikes.

The early-morning explosion along the main boulevard leading to the Kremlin also was linked to a double suicide bombing at a weekend rock concert in Moscow, which killed the two female attackers and 14 other people. The bombings raised fears Chechen rebels were bringing their separatist war to the Russian capital.

Interior Minister Boris Gryzlov said the two attacks were coordinated by a unit of terrorists ``with a common leadership,'' but he declined to identify the ringleaders.

``We have information that will enable us to shortly hunt down this unit training female suicide bombers,'' Gryzlov said in comments shown on Russian television.

All Russians, ``not only Muscovites, but also residents of other cities, should be vigilant,'' he said.

President Vladimir Putin's main envoy on Chechnya, Sergei Yastrzhembsky, warned earlier of an increased threat of such suicide bombings across the country.

``The threat of spreading of the 'Palestinian variant' of terrorism in Russia has become reality,'' he told an international conference in Rome, according to a Thursday report in Vremya Novostei newspaper.

Shortly before midnight Wednesday, police stopped a woman trying to carry a bag with explosives into a restaurant on Tverskaya-Yamskaya Street.

The woman was detained after her behavior attracted the attention of security guards, officials said. Her bag, which contained a bomb Gryzlov said was equivalent to 1.1 pounds of TNT, was left on the street.

After clearing the area and failing to trigger the device with a remote-controlled robot, a bomb disposal expert was called in.

As Federal Security Service Maj. Georgy Trofimov crouched down early Thursday in a protective suit to inspect the device, it detonated with a burst of smoke and sparks _ throwing him back several yards into the street.

Trofimov, 29, had helped defuse part of an explosives-laden belt worn by one of the two female bombers who died in Saturday's attacks at the rock festival. About 60 people were wounded.

A Moscow court issued an arrest warrant for 22-year-old Chechen resident Zarema Muzhikhoyeva, who was detained for the latest attack, ITAR-Tass reported. Her husband joined the Chechen rebels several years ago and was killed, and her family's house was destroyed in the earlier 1994-1996 Chechen war, the news agency said.

Muzhikhoyeva was living with her aunt in Chechnya but left five months ago and her whereabouts since were unknown, law enforcement officials told ITAR-Tass.

Worries about terror attacks in Moscow have remained high since militant Chechens _ including women wearing belts of explosives _ seized a Moscow theater in October. Russian special forces ended the standoff by pumping a narcotic gas into the building that later was blamed for causing most of the 129 hostage deaths.

The Kremlin insists the main fighting in Chechnya is over since the latest war there began almost four years ago, but small-scale attacks and mine explosions cause daily Russian casualties. Hundreds of civilians are each day detained in ``mopping-up'' operations to find rebel sympathizers.

Yastrzhembsky told the Interfax news agency on Thursday that the Kremlin refused to negotiate with separatist leader Aslan Maskhadov.

U.S. Ambassador to Russia Alexander Vershbow said Washington would share intelligence information with Moscow to help prevent terror attacks, Interfax quoted him as saying.

Still, the United States ``will continue to support efforts to find a political solution to the Chechen conflict, which at the end of the day is the only way to end the tragedy,'' Vershbow said.

Also Thursday, Chechen officials reopened the provincial government's administration building damaged in a December truck bomb attack that killed 72 people.

The Kremlin-backed Chechen leader, Akhmad Kadyrov, said the restored building was a symbol of Chechnya's rebirth in spite of terrorists' actions, ITAR-Tass reported.

Russian forces have been bogged down in Chechnya since 1999, when they returned after rebel raids on a neighboring region and a series of bombings in Russian cities. Russian troops fought a 1994-1996 war with Chechen separatists that ended in a Russian retreat and de facto independence for the region.