At least four Afghans were killed when protesters demanding better security clashed with riot police in Kabul Friday.
Witnesses say police fired live rounds into the air to disperse hundreds of stone-throwing demonstrators.
Public anger has been mounting since a devastating truck bomb explosion Wednesday at the beginning of the Muslim holy month of Ramadan. One of the worst attacks since 2001 killed 90 people and wounded more than 450 others.
More than a thousand demonstrators, many carrying pictures of bomb victims, gathered Friday near the site of the blast and marched toward the presidential palace, demanding the resignation of the Afghan government. Some protesters burned effigies of President Ashraf Ghani.
Riot police used water cannons and tear gas to push the protesters back and also fired live bullets over the heads of the crowd. Hospital workers say at least four people died.
International rights group Amnesty International denounced the police action as an "excessive and deadly response" and called for an investigation.
The United Nations Special Representative in Afghanistan, Tadamichi Yamamoto, appealed for restraint. "I strongly discourage any actor from seeking opportunistically to use these very emotional and fragile moments to destabilize the situation and risk further harm to civilians," he said in a statement.
No one has claimed responsibility for Wednesday’s truck-bomb attack, which Afghanistan’s intelligence agency has blamed the Taliban-allied Haqqani Network.
Most of those killed were civilians, but the casualty list also included members of Afghan security forces.