Afghans rioted for a second day over the burning of a Koran in the US, killing nine people in Kandahar and injuring more than 80 in a wave of violence that underscored rising anti-foreign sentiment after nearly a decade of war.
The desecration at a small Florida church has outraged Muslims worldwide and in Afghanistan it further strained ties with the West.
On Friday 11 people were killed, including seven foreign UN employees, in a protest in the northern city of Mazar-e-Sharif.
The protests come at a critical juncture as the US-led coalition gears up for an insurgent spring offensive and a summer withdrawal of some troops, and with Afghanistan's mercurial president increasingly questioning international motives and Nato's military strategy.
Two suicide attackers disguised as women blew themselves up and a third was gunned down on Saturday when they used force to try to enter a Nato base on the outskirts of Kabul, Nato and Afghan police said.
Earlier in the week, six US soldiers died during an operation against insurgents in eastern Afghanistan near Pakistan, where the Taliban retain safe havens.
President Hamid Karzai expressed regret for the 20 protest deaths, but he also further stoked possible anti-foreign sentiment by again demanding that the US and United Nations bring to justice the pastor of the Dove Outreach Centre in Gainesville, Florida, where the Koran was burned on March 20. Many Afghans did not know about the Koran-burning until Mr Karzai condemned it four days later.
The pastor, the Rev Terry Jones, had threatened to destroy a copy of Islam's holy book last year but initially backed down. On Friday he said Islam and its followers were responsible for the killings.
US president Barack Obama said desecration of the Koran was "an act of extreme intolerance and bigotry", but that did not justify attacking and killing innocent people, calling the UN compound attack "outrageous and an affront to human decency and dignity".
The protests began on Friday in Kabul, Herat in western Afghanistan and Mazar-e-Sharif, where thousands flooded the streets. In Mazar-e-Sharif, Afghan demonstrators stormed the UN compound, shooting dead four Nepalese guards, a Norwegian, a Romanian and a Swede. Afghan authorities suspect insurgents infiltrated the mob. More than 20 people, including a militant they suspect was the ringleader of the assault, have been arrested.