No delegates were harmed but at least two attackers were killed in fighting with Afghan security forces near the giant tent erected for the three-day gathering, officials said.

The Taleban claimed responsibility for the attack. The attack underscored the weak grip of Karzai's government in the face of the Taleban insurgency, which has strengthened despite record numbers of US forces in country.

"My dear Taleban, you are welcome in your own soil. Do not hurt this country, and don't destroy or kill yourselves," Karzai told the some 1,600 delegates in his opening address, which was broadcast nationally on state television.

But he said militants who caused the deaths of Afghans — an apparent reference to Al-Qaeda leaders — deserved no sympathy. "Those people who are killing innocents, punish them," Karzai said.

"Make peace with me and there will be no need for foreigners here," Karzai said.

About 10 minutes into his speech, Karzai was briefly interrupted by an explosion outside, which police said was a rocket. Karzai heard the thud, but dismissed it, telling delegates, "Don't worry. We've heard this kind of thing before."

Farooq Wardak, a government minister who is jirga chairman, said three militants dressed in burqas, carrying explosives and armed with guns and at least one grenade launched the attack from a building about one mile from the venue.

Two died in fighting and one was captured, he said.

However, Interior Ministry spokesman Zemeri Bashary said all three attackers were killed.

Delegates took a scheduled break for his departure, but did not return to their seats for about three hours, with some taking refuge beneath trees from the rocket attacks.