KABUL (REUTERS, WASHINGTON POST) - At least 12 people were killed, three of them children, and 20 others were wounded on Wednesday (Nov 13 ) when a van packed with explosives targeted a vehicle belonging to a foreign security company, Afghan security officials said.

There was no immediate claim of responsibility for the rush-hour attack, which came a day after the Afghan government agreed on a prisoner exchange with the Taleban insurgents in the hopes of reviving peace talks.

Nasrat Rahimi, a spokesman for the interior ministry, said a suicide bomber driving a van targeted an armoured vehicle that belonged to GardaWorld, a Canadian security company that saw four of its staff wounded in the attack.

"Seven Afghan civilians were killed in the explosion and 10 people, including four foreign nationals, were wounded," Rahimi said.

He did not disclose the nationalities of the four wounded, but a senior Afghan security official said they were either Indian or Nepalese nationals and Kabul police were currently working to identify the injured.

"We can confirm that GardaWorld employees were impacted by the attack that took place in Kabul earlier," GardaWorld said in a statement late on Wednesday. The company declined to give further information.

Officials in the foreign ministries of India and Nepal did not respond to requests for comment.

Two Taleban commanders and a leader of the Haqqani militant group were released in exchange for two professors, an American and an Australian, in a development some analysts had hoped could pave the way for stalled peace talks in Afghanistan.

The Taleban has so far refused to engage with the foreign-backed Afghan government, which the insurgent group calls a "puppet" regime.

One of the freed men, Anas Haqqani, is the younger brother of Sirajuddin Haqqani, the second-in-command in the Afghan Taleban hierarchy and leader of the Haqqani network, considered the deadliest faction of the Taleban and which has carried out some of the most brazen attacks in Kabul.

Wednesday's attack came during a relative lull in violence after September's presidential election. During polling there was a surge in attacks by the Taleban that killed 85 people in ballot-related violence across the country.

Nearly 4,000 civilians were killed or wounded in the first half of this year, including a sharp increase in the number of casualties caused by government and foreign forces, according to the United Nations.