KABUL (Reuters) - A bomb attached to a vehicle killed two members of Afghanistan’s independent human rights commission in Kabul on Saturday, the group said, as violence in the country rises despite a U.S.-brokered peace process.

The Afghanistan Independent Human Rights Commission (AIHRC) said in a statement that 24-year-old donor coordinator Fatima Khalil and 41-year-old driver Ahmad Jawed Folad were killed by an explosive device while in an AIHRC vehicle on the way to its office on Saturday.

“It is intolerable, assassinating human rights defenders is a war crime in the context of armed conflict,” the AIHRC said, adding that staff had previously been the target of attacks.

Kabul’s police spokesman confirmed that two people died in a blast early on Saturday.

No group claimed responsibility for the attack. A Taliban spokesman denied the group was involved.

It comes at a sensitive time amidst heightened violence around Afghanistan, including growing attacks against officials in urban centres.

The United States and other foreign players are trying to usher the insurgent Taliban and the Afghan government towards peace talks after the United States signed a troop withdrawal deal in February with the militant group to pave the way to ending more than 18 years of war.

Negotiations were expected to begin soon after progress was made on a dispute over the release of a controversial group of Taliban prisoners, Reuters reported on Friday.

However, a diplomatic source in Kabul said rising violence could hamper the peace process, and that foreign players were trying to appeal to the Taliban to reduce attacks.

The United Nations and foreign powers, including the United Kingdom and Turkey, condemned Saturday’s attack.

“There can be no justification for attacks against human rights defenders. Immediate investigation needed with perpetrators held to account,” the UN mission to Afghanistan said on Twitter.