By Hamid Shalizi and Mirwais Harooni
KABUL (Reuters) - A suicide bomber rammed his car into an Afghan army vehicle providing security for a compound where Afghanistan's political and tribal elites are due to gather next week to debate a security pact with the United States.
Saturday's attack took place just hours after President Hamid Karzai called on the Taliban to take part in the Loya Jirga assembly that convenes on Thursday to decide whether to allow some U.S. troops to stay in Afghanistan after 2014.
At least six people were killed and 22 wounded in the blast, said Sediq Sediqqi, an Interior Ministry spokesman. He said the casualties were a mix of soldiers and civilians.
The blast occurred shortly after 3 p.m., fewer than 100 meters (yards) from a huge tent where more than 2,000 prominent Afghans are due to gather, a Reuters witness said.
No one immediately claimed responsibility for the attack.
One man fleeing the bombing, Mohammad Amin, looked dazed as he described to Reuters seeing a white Totoya Corolla vehicle speed towards a police checkpoint and then explode.
Covered in blood and dust, he said he was standing across the street behind his parked car when the blast occurred.
"Thank God my car protected me because it was so close. My ears are still ringing," Amin said.
A Reuters reporter saw at least six wounded people, as well as a large unchecked fire and numerous smashed cars.
A Kabul police spokesman, Hashmat Stanekzai, said earlier there were at least 15 dead and wounded as a result of the attack, but could not immediately provide more detail.
A loya jirga is a traditional Afghan meeting convened to debate matters of national importance and includes thousands of tribal elders, politicians and other elites.
For almost a year, Washington and Kabul have been seeking to conclude a Bilateral Security Agreement that will help determine how many U.S. soldiers and bases remain in Afghanistan after most foreign combat troops exit by the end of next year.
The lack of agreement has raised the prospect that Washington may yet pull out all of its troops next year unless differences are ironed out.
Senior U.S. and NATO officials said last month they were confident Afghanistan's elders and parliament would back the deal allowing American troops to stay after 2014.
Two years ago, the United States ended its military mission in Iraq with a similar "zero option" outcome after the failure of talks with Baghdad.
Earlier on Saturday, Karzai called on the Taliban, who have been waging an insurgency against his government and U.S.-led forces for over a decade, to put down their guns and participate in the assembly.
"We hope by all means that they participate in the Loya Jirga," said Karzai, who is keen to find a negotiated political solution to years of fighting with the Taliban. "They are our countrymen and they have the right to be part of such meetings."
"I once again invite them to please come and participate in the people's national meeting."
(Writing by Dylan Welch and Maria Golovnina; Editing by Alison Williams)