Gunmen have stormed the British Council office in the Afghan capital, Kabul, killing at least 12 people and taking over the compound for hours.
A suicide car bomb destroyed the compound wall and a number of heavily armed men forced their way inside.
After several hours of gunfire and blasts, the UK's ambassador in Kabul said all the gunmen had been killed.
The Taliban said the attack marked the anniversary of Afghanistan's independence from the UK in 1919.
There has been some confusion about the number of people killed in the Kabul attacks.
At least eight Afghan policemen and a New Zealand special forces soldier were killed, officials from both countries said. Three security guards also died, the Afghan interior ministry told the BBC.
UK Prime Minister David Cameron condemned the "cowardly attack", saying he had spoken to New Zealand Prime Minister John Key to thank him for the role the country's special forces had played in defending the compound.
The US secretary of state called the attack "vicious" and said the country offered its condolences to the families and loved ones of all those killed and injured.
"Brutal attacks such as these will not lessen our resolve or our commitment to Afghanistan and the region," Hillary Clinton said in a statement.
"The United States will continue to support the Afghan people and to assist the Afghan government, security forces, and civil society as they rebuild after decades of war," she added.
The UK Foreign Office said all British citizens were "shaken but well" after being safely removed from the building.
One British and one South African teacher were among four residents of the compound who took refuge in a reinforced safe room during the attack, the British Council said.
British ambassador William Patey said there were injuries among the Nepalese ex-Gurkha soldiers guarding the compound, but none had died, AFP reported.
Friday's strike was a three-phase attack, intelligence sources told the BBC. First, a suicide attacker detonated his explosive vest at a square in western Kabul where police were guarding a key intersection shortly after 05:30 (01:30 GMT).
Ten minutes later, a suicide car bomber detonated his vehicle outside the front gate of the British Council, destroying a wall, which allowed the attackers into the compound.
A number of Afghan policemen were feared to have been buried in the rubble.
As the area was evacuated, local shopkeepers said as many as nine insurgents armed with rocket-propelled grenades, heavy machine guns and AK-47s started firing as they ran towards the British Council building.
Afghan and Nepalese guards fought the attackers until help arrived in the form of Afghan commandos and New Zealand special forces.
A lone injured gunman managed to hold out in an area protected by armoured doors and glass before was he killed eight hours after the attack began, Afghan intelligence officials said.
Police sources earlier told the BBC they believed the suicide attackers had "brought enough weapons to fight for a day".
There were reports that the country's national intelligence agency had warned the interior ministry of an imminent attack around midnight last night.
The intelligence suggested that a suicide bomber and at least two vehicles were attempting to make their way from Kabul's Paghman district to the centre of the city to carry out an attack. Police sources said the intelligence was not very specific and did not provide the location of the intended target.
"They managed to enter in the early hours of morning," intelligence and police sources said. "Most of them were wearing burkas, posing as a family. In our tradition and culture, it is impossible to search women."
Condemning the "despicable attack", British Foreign Office Minister Alistair Burt said: "My thoughts are with those killed and injured and their families and friends, including locals working to protect the British Council building.
"It is due to the presence of mind of the staff involved and our good security measures that no British nationals were hurt," said Mr Burt.
"This attack, against people working to help build a better future for Afghanistan, will not lessen the UK's resolve to support the Afghan people."
The British Council is a partly government-funded agency that runs mainly cultural programmes.
Martin Davidson, chief executive of the British Council, said the attack on its Kabul office "must not and will not" prevent it from giving young Afghans the support they need.
The Afghan authorities earlier stepped up security in the capital, amid fears an attack could be imminent on the public holiday.
However, the Taliban have recently shown that they can strike pretty much anywhere in Afghanistan, says the BBC's Quentin Sommerville in Kabul.