Kabul Police Chief Ayoub Salangi said a man with a remote device was captured near the site and badly beaten by irate residents after the incident.
Tuesday’s attack came not long before Afghanistan’s defense minister officially stepped down from his post after being disqualified by parliament for not taking action against protracted shelling from Pakistan.
The intended target of the bombing could have been a group of Afghan forces passing the bridge at the time of the blast, the Interior Ministry said. The troops escaped unhurt.
The victims were all locals, not visitors who often come to the area for picnics, the ministry said. Some civilians were wounded by the explosion.
There was no immediate claim of responsibility, but officials blamed Taliban-led insurgents. The blast may add to growing concern among civilians and comes weeks after nearly 20 civilians were killed by Taliban suicide bombers targeting a picnic spot in Qargha, which lies near Paghman.
Although Kabul has been the scene of repeated commando-style raids, including the Qargha strike, roadside bombs have been uncommon in the capital and its surroundings areas until recently.
Last week, six civilians were killed by a roadside bomb near the main U.S. base in Bagram, which lies on a main road leading north from Kabul. Days later, a magnet bomb targeted an army vehicle in the city.
Roadside bombs are the Taliban’s favored weapon in its campaign against foreign and Afghan forces, and most bombings occur in Afghanistan’s east and south, the main strongholds of the militants. Civilians, however, are the most common victims of such attacks.
Defense Minister Abdul Rahim Wardak announced his resignation at a brief news conference.
“On the basis of the decision by the country’s parliament, the highest legislative institution, and by seeking permission from the presidential authority, I announce the end of my duty as defense minister,” he said.
President Hamid Karzai has yet to announce successors to Wardak and Bismillah Khan Mohammadi, the interior minister, who also lost his job in a no-confidence vote by the parliament Saturday.
Wardak and Mohammadi both have served for most of the past decade of the U.S.-led war as the country’s key security officials. Their departure comes amid an expansion of attacks by the Taliban-led insurgents and the transition of security responsibility to Afghan forces from the foreign troops who are set to leave Afghanistan by 2014.
Also Tuesday, at least two foreign soldiers lost their lives in separate attacks when a suicide car bomber hit a joint NATO and Afghan base south of the capital. Several foreign troops and a group of Afghan civilians working inside the base were wounded, officials said.