US President Barack Obama and President Hamid Karzai on Wednesday deplored an explosion of violence in Afghanistan over the torching of a Koran by an American pastor, after a sixth day of protests.
The two leaders held an hour-long video conference to discuss the wave of demonstrations against last month's burning of a Koran at a church in Florida which have left at least 24 dead, including seven United Nations employees.
Protests continued for a sixth day Wednesday, while a woman died in a car crash involving a NATO military convoy in the Afghan capital Kabul, triggering a demonstration in which stones were thrown at the international forces.
The White House said that "both leaders deplored the desecration of the Koran, strongly condemned the April 1 attack on (the United Nations compound) in Mazar-i-Sharif and expressed deep regret for the tragic loss of life."
"The two presidents were clear that to attack and kill innocent people is an affront to human decency and dignity," it said.
But tensions between Karzai and his Western allies have been growing in recent months, and a statement from the Afghan president's office differed in nuance to the US interpretation.
The Afghan statement said the presidents discussed "the desecration of the Koran by the American pastor and the subsequent unpleasant incidents that followed in Afghanistan."
It said that Obama had "strongly condemned the desecration of the Koran by an American pastor and regretted the casualties at protests in Mazar-i-Sharif and Kandahar."
It reiterated that Karzai would investigate the violence.
The White House has this week called the burning "un-American", after Obama had earlier branded it an act of "extreme intolerance and bigotry."
There has been little violent reaction in the rest of the Islamic world to the Koran burning, but protests began in Afghanistan eight days after Karzai condemned it as "disrespectful and abhorrent."
The violence comes as Afghan forces are due to assume control of security in a handful of Afghanistan's safer areas -- including Mazar-i-Sharif -- from July, allowing limited foreign troop withdrawals to begin.
Around 130,000 international troops, some two-thirds of them from the United States, are in Afghanistan fighting a nearly 10-year Taliban insurgency. Afghan forces are due to take complete control across the country in 2014.
Obama and Karzai also discussed progress in the transition, the White House said.
In Afghanistan's southern Zabul province, around 1,500 people gathered in the town of Qalat for a peaceful demonstration over the Koran burning, deputy provincial governor Mohammad Jan Rasoulyar said.
And in Nimroz province in the southwest, hundreds more protested, shouting anti-American slogans and throwing stones at police in Dilaram district. No-one was injured, said deputy provincial police chief Musa Rasouli.
The road accident in Kabul left one woman dead and another woman and a child wounded, according to city police spokesman Hashmat Stanikzai.
"The wounded were taken to hospital. People gathered at the accident site and started throwing stones at the military convoy. After the crowd started forming and throwing stones, the convoy left the area," he added.
The NATO-led International Security Assistance Force (ISAF) confirmed that one civilian had been killed and two wounded in the crash but stressed: "No shots were fired by ISAF service members."
It did not comment on the nationality of the troops involved, but local police said they were British.
Elsewhere in the troubled country, seven insurgents were killed overnight after launching a rocket attack on a military airport in the eastern city of Jalalabad, where the local provincial governor was present.
Also in the east, an ISAF spokesman said that at least 80 insurgents and six international troops had been killed over the last ten days in the strategically crucial Kunar province, which borders Pakistan.
He did not give further details of the operations being carried out, but Pakistan's border areas are used as rear bases by insurgents.
Separately, ISAF said that two international troops had died in a friendly fire incident in the south of the country. It did not identify their nationality.