KABUL  - A suicide car bomb blew up Monday outside a US military base in eastern Afghanistan, killing ten civilian labourers, as the country marked Independence Day under the shadow of extremist attacks. The blast, claimed by the insurgent Taliban, did not penetrate the base in the town of Khost and security forces were able to prevent a second suicide attack moments later, the US-led coalition and Afghan officials said. It came amid massive heightened security as Afghanistan marked Independence Day, commemorating its final defeat of the British army in 1919. Kabul was locked down with 7,000 police on patrol and checkpoints at nearly every city centre intersection and main entry points into the capital. President Hamid Karzai's annual Independence Day address in the stadium was called off with no explanation with a small commemoration due later in the day. A spokesman for the Taliban, Zabihullah Mujahed, said it carried out the suicide attack in Khost, 30 kilometres from the border with Pakistan. The US-led coalition said insurgents detonated the device outside the base and that nine Afghans were killed and 13 wounded. A secretary to the Khost governor, Mohammad Bilal, gave the same toll. "It was a suicide car bombing against the gates of the Salerno camp," he said. "Moments later a second car bomber came and wanted to detonate his bombs. Police identified him and opened fire on him," Bilal added. He said the attacker was able to escape into the crowd and security forces destroyed the second bomb. "They wanted to disturb Independence Day," he added. The dead and wounded were labourers who had been waiting to enter the base for work, provincial government spokesman Khaibar Pashtun said. Reacting to the suicide bombing, Karzai said in a statement that by killing "innocent civilians on Independence Day, the terrorists showed their hostility to the freedom of Afghan people." In fresh violence Monday, a mine blew up a police vehicle in the province of Nangarhar and killed two policemen, an official said. Meanwhile, an Afghan woman and two children were killed when British soldiers fired rockets at a compound in southern Afghanistan over the weekend to thwart a Taliban attack, the British military said Monday. The British military statement said: "An Afghan woman and two children died in the Sangin area when UK forces fired rockets at Taliban fighters, unaware that civilians were in the vicinity of enemy fighters in a local compound."