At least 16 people, including both Afghans and foreigners, were killed when a suicide bomber blew himself up near a popular Lebanese restaurant in the Afghan capital Kabul police have said.
Ari Gaitanis, a spokesman for the United Nations, said late on Friday four UN civilian personnel, who were reportedly near explosion scene at the time of the attack, remained unaccounted for.
Taliban fighters claimed responsibility for Friday's attack in the Wazir Akbar Khan district, which hosts many embassies and restaurants that cater to expatriates.
|Four UN workers unaccounted for after Kabul suicide bombing.
"More than 13 people were killed, Afghan and foreigners," said Mohammad Zahir, Kabul's police chief, adding that the nationalities of the foreign casualties were not immediately clear.
At least four women and ten Afghans were killed in the blast at Taverna du Liban, one of three Lebanese restaurants in the city. A Taliban spokesman said that those killed were German nationals.
Al Jazeera's Jane Ferguson, reporting from Kabul, said that the attack was a significant "breach of security" in the area of Kabul.
At least three attackers were reportedly involved, including the suicide bomber and two other gunmen, who then entered the restaurant following the blast, and gunned down the diners, our correspondent said.
"The scenes inside the restaurant is quite incredible," she said. "Anybody inside seems unlikely to escape from the gunmen.
In Berlin, the German foreign ministry said it could not confirm that Germans were involved but the crisis team of the German government had been activated to shed light on the incident.
The assault was carried out around dinner time in the heavily fortified district where many wealthy Afghans also live.
Bursts of gunfire followed the attack.
"First there was a suicide attack near a restaurant for foreigners where a man detonated his explosives attached to his body, and then possibly one or two insurgents entered the restaurant," one Afghan security source said.
The taverna has steel doors and customers have to pass through security to get in, as is the case with many restaurants in Kabul.
Some officials suggested fighters were still inside the venue but no gunfire could be heard more than an hour after the attack and it was unclear if any customers were still inside.
Hashmat Stanekzai, a spokesman for Kabul police, said an operation to clear the building was under way.
"The clearance operation is still ongoing. Our security forces are not inside the restaurant yet," he said.
"There might be some insurgents inside so we have to act carefully to avoid possible casualties."
The attack came at a tough time for Afghanistan as most foreign forces prepare to leave the country this year after more than a decade of war and almost daily attacks.
Negotiations have stalled on a security accord that would allow some US and NATO troops to stay after 2014.
The bilateral security agreement (BSA) would see several thousand US troops remain in Afghanistan to provide training and assistance in the battle against the Taliban.
Security concerns have been also rising ahead of an April presidential election when Afghans will vote to choose a successor to President Hamid Karzai, an event likely to be targeted by the Taliban.
On Friday night, gunfire continued for about 20 minutes after the initial blast and the main road leading to the area was cordoned off.
Interior Ministry spokesman Sediq Sediqi said three suicide bombers approached the building, one of whom detonated his bomb. The other two were shot by security forces, he said.
A series of attacks in 2013 targeted foreign compounds, the Supreme Court, the airport and the presidential palace in Kabul.