At least seven people have been killed in protests around Afghanistan against the burning of Korans at a US air base.
The latest violence raised the total number of people killed since the protests broke out to 20.
The governor's office in western Herat province said six died in three incidents there.
Three people were killed when a truck full of ammunition exploded after protesters set it ablaze. Three others died in two separate incidents when armed men among the protesters exchanged gunfire with security forces.
Another protester died when Afghan security forces fired in the air to prevent demonstrators from storming a Hungarian base in the north.
Thousands joined new demonstrations in a clear sign that President Barack Obama's apology has failed to quiet the outrage over the incident. Afghan security forces were put on high alert.
About 4,000 protesters marched toward the governor's compound in Khost, the capital of Khost province, police said. In the eastern part of Nangarhar province, several thousand shouted "Death to America" and burned a cardboard picture of Mr Obama.
In the capital Kabul, about 100 protesters gathered near the ministry of defence but scattered when Afghan soldiers fired in the air.
"We don't care about Obama's apology," said Kamaluddin, a 25-year-old Kabul protester. "We have to protest to be responsible to our god. They are burning our Koran. An apology is not enough."
US General John Allen, the senior commander of US and Nato troops in Afghanistan, said an investigation into the burning incident at Bagram Air Field was under way and called on Afghans to be patient and exercise restraint.