KABUL — A suicide bomber blew up a car packed with explosives near a busy market and a mosque in eastern Afghanistan on Tuesday, killing at least 89 people in the deadliest insurgent attack on civilians since the 2001 US-led invasion.
The blast destroyed numerous mud-brick shops, flipped cars over, and stripped trees of their branches, brutally underscoring the country’s instability as US troops prepare to leave by the end of the year and politicians in Kabul struggle for power after a disputed presidential runoff.
General Mohammad Zahir Azimi, the Defense Ministry spokesman, said the bomber detonated his explosives as he drove by the crowded market in a remote town in Urgun district, in the Paktika province bordering Pakistan. Azimi gave the death toll and said more than 40 other people were wounded.
Nearby hospitals were overwhelmed, and dozens of victims were transported over dangerous roads to the capital, Kabul.
Ahmad Shah, a gas station employee who rushed to the site to help, said he loaded dozens of people who were injured or killed into vehicles.
‘‘I saw the smoke, and the town was burning. There were dead bodies everywhere,’’ he said outside a hospital in Kabul.
Associated Press video footage of the aftermath showed mounds of twisted debris and the charred shells of cars flipped over on top of one another. Azimi said more than 20 shops and dozens of vehicles were destroyed.
Many victims were buried in the rubble, said Mohammad Reza Kharoti, administrative chief of Urgun district.
‘‘It was a very brutal suicide attack against poor civilians,’’ he said. ‘‘There was no military base nearby.’’
There was no immediate claim of responsibility, and the Taliban issued a statement denying involvement, saying they ‘‘strongly condemn attacks on local people.’’ Several other insurgent groups operate in Afghanistan.
The UN mission in Afghanistan said initial reports ‘‘suggest that the attacker prematurely detonated after police detected the explosives in his vehicle.’’
Several witnesses said the driver was in a four-wheel-drive vehicle and hit two vehicles parked on the edge of the market, leading police to open fire. Then the explosion happened.
Abdul Khan, who is from the area, rushed to the hospital in Kabul to donate blood. ‘‘Most of the people in the town lost three to four family members,’’ he said, adding his cousin had been killed.
It was the deadliest insurgent attack against civilians since the US invasion that ousted the Taliban in 2001. It exceeded the toll from twin bombings Dec. 6, 2011, that targeted Shi’ite Muslims and killed 80 people in Kabul and Mazar-i-Sharif.