Two security guards working for the Afghanistan Independent Human Rights Commission were killed in the eastern city of Jalalabad on Monday when a roadside bomb blew up as their vehicle passed, a police official said.

The provincial head of the AIHRC, which monitors human rights in Afghanistan, was in the vehicle when the bomb detonated, Nangarhar police spokesman Hazrat Hussain Mashriqiwal said.

Nicholas Haysom, head of the United Nations Assistance Mission in Afghanistan, condemned the attack, the latest in a wave that has intensified this year as the insurgency against the Western-backed government in Kabul has spread.

"The climate of fear created by such attacks threatens vital human rights work carried out throughout Afghanistan," he said in a statement.