Afghan security forces assist an injured man at the site of an explosion in Kabul, Afghanistan, Friday, Jan. 17, 2014. Afghan police said a suicide bomber attacked a Kabul restaurant popular with foreigners, officials. Afghan police forces assist an injured man at the site of an explosion in Kabul, Afghanistan, Friday, Jan. 17, 2014. Afghan security forces arrive at the site of an explosion in Kabul, Afghanistan, Friday, Jan. 17, 2014. Afghan police said a suicide bomber attacked a Kabul restaurant popular with foreigners, officials. (AP Photo/Massoud Hossaini) Afghan security forces arrive at the site of a suicide attack in Kabul, Afghanistan, Friday, Jan. 17, 2014. Afghan police say a suicide bomber has attacked a restaurant in central Kabul that is popular with officials, foreigners and business people. There were reports of casualties. KABUL, Afghanistan (AP) - A suicide bomber blew himself up outside a Kabul restaurant filled with foreigners and affluent Afghans, while two gunmen snuck in through the back door and opened fire Friday in a brazen dinnertime attack that killed 16 people, officials said. The fatalities included four U.N. personnel. The Taliban claimed responsibility within an hour of the attack against La Taverna du Liban, part of a stepped-up campaign of violence against foreign and government interests to send a message that the militants are not going anywhere as the U.S.-led coalition winds down its combat mission at the end of the year. The bombing served as a reminder that although militant violence in the capital has dropped off in recent months, insurgents remain capable of carrying out attacks inside the most heavily guarded areas. Security officials, speaking on condition of anonymity because they were not authorized to release the information, said the assault began with the suicide bomber detonating his explosives at the front door of the restaurant, located in an area housing several embassies, non-governmental organizations and the homes and offices of Afghan officials. As chaos ensued, the two other attackers entered through the kitchen and began shooting. They were later killed by security guards, said Interior Ministry spokesman Sediq Sediqi. Kabul police chief Gen. Mohammad Zahir Zahir said the 16 people killed were all inside the restaurant. He said foreigners and Afghans were among the dead, but he did not provide a breakdown. Officials said at least four other people were wounded. Four United Nations personnel were among those killed, U.N. Secretary-General Ban Ki-moon said. The four were not identified. Ban condemned the attack "in the strongest terms," saying "such targeted attacks against civilians are completely unacceptable and are in flagrant breach of international humanitarian law," U.N. deputy spokesman Farhan Haq said. The International Monetary Fund's representative in Afghanistan, Wabel Abdallah, also was among those killed, IMF chief Christine Lagarde said in a statement. The 60-year-old from Lebanon was appointed to the position in 2008. Britain's Foreign Office confirmed late Friday that a British national was among the dead. In Washington, State Department spokeswoman Jen Psaki said the U.S. condemns "this despicable act of terrorism in the strongest possible terms." She said information about the attack was still coming in, but that all U.S. Embassy personnel were accounted for. Deputy Afghan Interior Minister Ayoub Salangai said in a tweet that the dead included four women. The restaurant, like most facilities that are frequented by foreign diplomats, aid workers, journalists and businessmen in the war-weary country, has no signs indicating its location and is heavily secured. It sits on a small side street just off a bumpy semi-paved road in a house with low ceilings and an enclosed patio but no windows. Bags of dirt are piled up around it to act as blast walls, and guests must go through a series of steel airlocks, where they are searched, before entering. The surrounding area is full of police and security guards to protect against insurgent attacks, which have increased in recent months around the country. Police at the scene did not allow reporters near the restaurant, located in the diplomatic quarter of the central Wazir Akbar Khan area, as they rushed to help the wounded and ensure there were no more gunmen. Taliban spokesman Zabihullah Mujahid claimed responsibility for the attack, which he said targeted foreign officials dining at what he described as a "hotel." There was a suicide attack on a foreign hotel where special foreign invaders are coming for dinner. In this attack an explosive was used which was very strong and heavy casualties and massive destruction happened," he said. Zabihullah said the targets of the attack included "high-ranking German officials." In Berlin, the German Foreign Ministry said it was looking into the report. The Taliban frequently provide exaggerated casualty figures. There have been a number of attacks in Kabul so far this month, including a suicide bicycle bombing of a bus carrying police that killed two people. The last major attack near a foreign facility, a heavily fortified guest house in Kabul, took place on Oct. 13, when a suicide car bomber killed two passers-by. That facility, knows as Green Village, was also attacked in 2012, killing seven guards and civilians. Insurgents have frequently targeted foreign interests around the country and in Kabul. The Taliban have increased their attacks in recent months after foreign forces handed over control of security for the country to the Afghan army and police. Foreign forces are scheduled to withdraw from the country altogether by the end of this year. A security agreement that would keep about 10,000 U.S. troops and about 6,000 from allied nations past 2014 has been stymied by President Hamid Karzai's refusal to sign it until Afghans elect his successor in the April 5 elections. The deal is seen as crucial to train and mentor the nascent Afghan security forces, which now number about 350,000. If the deal falls through, the U.S. has said it will pull all its forces out of Afghanistan.