|Mob violence erupted at the demonstration on Friday [Al Jazeera]
United Nations officials have condemned the killings of the organisation's staff during a protest over the burning of the Quran by a US preacher.
Nestor Osorio, UN Security Council president, spoke on behalf of the 15-nation body in denouncing the deaths and expressing condolences to families of the victims.
"The members of the Security Council condemned all incitement to and acts of violence," said Osorio on Saturday.
"They called on the government of Afghanistan to bring those responsible to justice and take all possible steps, with the assistance of the International Security Assistance Force, as appropriate, to protect UN personnel and premises.
"The members of the Security Council reaffirmed their support for the people and the Government of Afghanistan, their support for the crucial work that the United Nations is doing in partnership with the Government for the benefit of all Afghans, and the Council’s commitment to a secure and stable Afghanistan."
Afghan officials said at least 11 people were killed, including seven UN staff, at a United Nations operational centre in the northern city of Mazar-i-Sharif. A UN official said that some of the attackers were killed by security guards.
The attack appears to be the deadliest against the UN in the country since the 2001 invasion.
Demonstrators stormed the UN office on Friday, opening fire on guards and lighting fires inside the compound after gathering to protest over reports that an evangelical pastor last month burned a copy of the Muslim holy book in Florida.
In a statement, the UN said three civilian workers and four security personnel were killed - none of which were from Afghanistan. A UN official also told the Associated Press news agency that seven workers and four Afghan protesters have been killed. An estimated 20 other demonstrators were injured.
The mission at Mazar-i-Sharif is now being evacuated.
Afghan police earlier put the death toll at eight UN workers and four Afghan protesters. Two of the UN staff members were beheaded, according to police, though details of the killings are unclear.
Al Jazeera's Hashem Ahelbarra reported from Kabul that people converged outside the UN mission soon after the midday prayers.
The mission is one of the backbones of UN operations in the country, he said. Some of the protesters were armed with knives, and the chief of the mission was badly injured in the attack.
"The protests degenerated into a very violent attack," he explained.
Protests 'gave cover'
Ata Mohammad Noor, the governor of Northern Balkh province, said insurgents used the protests as cover to attack the UN office.
|Terry Jones' "Judge the Quran day" drew
widespread international condemnation
"The insurgents have taken advantage of the situation to attack the United Nations compound," Noor said.
Noor said Nepalese Gurkha guards were among those killed. He said the guards worked for a private security firm.
The UN has not yet announced the nationalities of those killed. The Taliban has claimed responsibility for the violence, saying it was the first step in a campaign against the upcoming presidential elections.
Afghan officials said about 2,000 people peacefully gathered outside the UN office, until some members of the crowd grabbed weapons from the UN guards, opened fire on the police and stormed the building.
Farhan Haq, a spokesperson for the UN Secretary General Ban Ki-moon, spoke with Al Jazeera from New York.
Ban is seeking more information on the attack, and considers it "a cowardly attack which no circumstances could justify," Haq said on Friday.
Stephane de Mastura, the head of the United Nations Assistance Mission in Afghanistan (UNAMA), was travelling to Mazar-i-Sharif on Friday to investigate what had happened, he added.
UN assistance to Afghan people
The UN staff in Mazar-i-Sharif works in a range of areas, including electoral support, political advice, humanitarian aid, reconstruction and development.
"All of this is designed to provide as much assistance as possible to the Afghan people, which is what makes it so unjustified that this office was attacked," the spokesperson said.
Terry Jones, an American pastor, created a storm of controversy after he announced that he would burn copies of the Quran on the anniversary of the September 11 attacks last year. Under pressure from political leaders, Jones "suspended" the event.
However, on March 20, Jones oversaw the burning of a copy of the Muslim holy book by another pastor, Wayne Sapp.
The worst previous attack on UN workers in Afghanistan was an insurgent assault on a guesthouse in October 2009. Five UN staffers were killed and nine others wounded.
UN staff have been targeted in other countries, including a bomb attack on the UN compound in Algiers in December 2007 which left 17 dead.
The bombing of a hotel in Baghdad in August 2003 where the UN mission had its headquarters took the lives of at least 22 people, including UN special envoy to Iraq, Sergio Vieira de Mello.