A suicide bomber blew himself up near a NATO base in Kabul\'s heavily-fortified diplomatic district on Wednesday, killing two Afghan security guards and wounding two government officials, police said. The Taliban, leading an insurgency against US-led troops and the Afghan government, claimed responsibility and said the target was a CIA office. \"One suicide attacker and two security guards were killed in the attack and one security guard was injured,\" Kabul police chief Mohammad Ayoub Salangi told AFP, dismissing reports that a second bomber was involved. \"Two members of the defence ministry who were inside their car parked at the site of the attack have also been wounded.\" Salangi said the bomber, who was wearing a security guard\'s uniform and was carrying an automatic rifle and grenades, came under fire but managed to detonate his explosives. Shrapnel hit a passing vehicle of NATO\'s International Security Assistance Force but no personnel were injured, a spokesman said. \"All ISAF bases in the green zone are secure,\" he added. The blast was heard across the capital\'s diplomatic district, prompting the US embassy to sound its \"duck and cover\" alarm. An AFP photographer saw three bodies, including that of the bomber, near Camp Eggers, a major NATO military base in the zone. The target remained unclear but the police chief said the bomber was trying to enter a tall building under construction. Insurgents have used similar sites in the past from which to launch grenade and machinegun fire on nearby targets. The Taliban said in a text message to AFP that \"a large number of fedayeen (suicide bombers) armed with light and heavy weapons attacked an important office of the CIA in the centre of Kabul and the fighting is continuing\". \"The enemy has suffered heavy losses but a precise number can\'t be determined at this time.\" The Islamists regularly exaggerate claims in their insurgency against the government of President Hamid Karzai, which is backed by more than 100,000 NATO troops. The attack came amid increased security in Kabul before the Shiite holy day of Ashura on Saturday. Last year a suicide attacker killed 80 people attending Ashura day ceremonies at a shrine in the capital. Suicide attacks are a Taliban trademark, along with roadside bombs. While the fighting is concentrated in the south and east of the country, Kabul has been hit by a series of deadly suicide and commando-style insurgent attacks this year. Among the major assaults, explosions and gunfire rocked the city on April 15 as squads of Taliban suicide attackers struck across Afghanistan. At least 51 people were killed in the attacks, 36 of them insurgents. On June 22 Taliban militants armed with automatic weapons and rockets attacked a hotel near Kabul, seizing dozens of hostages and killing at least 18 people. And on September 8 a teenage suicide bomber struck outside NATO headquarters in Kabul, killing six people, including child hawkers, as Afghanistan marked a public holiday. Ten days later, a suicide car bomber killed 12 people including eight South Africans on a highway leading to the international airport. Earlier this month several rockets struck near Kabul\'s presidential palace and airport, killing one and wounding three, police said.