Six people were killed in an attack by suspected Taliban insurgents on the US embassy and NATO buildings in Kabul that ended Wednesday after 21 hours of clashes, officials said. Gunmen with suicide vests attacked several locations in Kabul Tuesday, with several firing from a 13-storey building near the embassy and the headquarters of the NATO-led International Security Assistance Force (ISAF). Two civilians and four policemen were killed in the ensuing clash, said General Ayoub Salangi, chief of the Kabul police. Nine insurgents were also killed across the city, he said. As many as 23 people including 11 policemen were wounded in the assaults, he was quoted as saying by the German Press Agency "DPA". The attacks started at 1:30 pm (0830 GMT) on Tuesday, and ended early Wednesday morning when special forces killed the last suspected assailant, who had been holed up for more than nine hours, another police official said. Security forces had cordoned off the area around Abdul Haq square, where other embassies, and national government agencies are also located. A police official at the site said they were combing the area for more explosives. "Six terrorists have been killed (in the building near the NATO headquarters)," Interior Ministry spokesman Sediq Sediqqi said early Wednesday. "We have secured the entire building. The clearing operation is over." US embassy spokeswoman Kerri Hannan confirmed the embassy had come under attack. "Four Afghans were injured in the attack on the embassy compound, none with life-threatening injuries," Hannan said. "They included three Afghan visa applicants and one local contract guard." Another suspected insurgent on Tuesday also attacked a border police headquarters in western Kabul but was killed by local forces. Another bomber was shot dead by police in the Kart-e-Sey area of the city, near the parliament and the Russian embassy. One more suspected attacker was also killed on the airport road by Afghan forces. The Taliban claimed responsibility for all the attacks. ISAF said six of its personnel had been injured. "Afghan security forces responded bravely, contained the insurgents, and systematically eliminated the threat," ISAF commander John Allen said in a statement. "The insurgency has again failed."