Update 02:27 a.m. EDT: A suicide car bomber targeted a convoy of foreign troops in the Afghan capital during rush hour-traffic on Sunday, flipping an armored vehicle on its side, but the number of casualties was unknown.
Taliban insurgents claimed responsibility for the attack in the city center which broke a period of relative calm in Kabul after a series of bombings in August.
TV footage showed an armored vehicle on its side as Afghan security forces cordoned off the street in the Joi Sheer neighborhood.
"It was a suicide bombing against a foreign forces convoy in a crowded part of the city and there are casualties," said Najib Danish deputy spokesman for the interior ministry.
Danish did not specify whether there were casualties among the foreign forces.
The headquarters of the international Resolute Support Mission in Kabul did not immediately confirm details of the attack, but a spokesman said it was verifying reports.
The Taliban insurgents fighting to topple the foreign-backed Kabul government claimed responsibility for Sunday's attack, saying it killed a number of foreign troops.
The group typically inflates casualty figures they inflict on Afghan and coalition forces.
The attack came during a period of heightened tension following intense fighting between government troops and the Taliban around the northern city of Kunduz, which fell briefly to the insurgent Islamist movement at the end of last month.
Fighting between government forces and the Taliban continues on the outskirts of Kunduz.
KABUL (Reuters) - A loud explosion rocked the center of the Afghan capital on Sunday after an apparent suicide attack against a convoy of foreign troops, a security official said.
The official, speaking on condition of anonymity, said initial reports suggested a suicide attack.
"It was during rush hour and there are casualties," he added.
The attack in Kabul came during a period of heightened tension following intense fighting between government troops and the Taliban around the northern city of Kunduz, which fell briefly to the insurgent Islamist movement at the end of last month.
(Reporting by Hamid Shalizi; writing by James Mackenzie; editing by Nick Macfie)