KANDAHAR (AFP) - Militants fired rockets at Natos main base in southern Afghanistan for the second time in less than two weeks and caused minor injuries, a US military official said Friday. Four rockets were fired at Kandahar Air Field on Thursday - two at around 3:00 pm (1030 GMT), one at 8:00 pm and another two hours later, the official told AFP. The one at 8:00 pm caused some minor injuries to multiple forces, the official said on condition of anonymity and without revealing nationalities of the troops involved. A rocket and ground attack on the Kandahar base wounded a number of people and forced a security lockdown on May 22. Kandahar Air Field is one of the largest military bases in Afghanistan and the principle Nato hub in the south. It regularly comes under rocket fire. It sits on the edge of Kandahar city, where US, Nato and Afghan troops are building an operation aimed at squeezing the Taliban out of their spiritual home after nine years of war. The Talibans insurgency against the government and 130,000 US-led foreign troops is now at its deadliest. The Islamist group last month vowed to unleash a new campaign of attacks on diplomats, lawmakers and foreign forces. On May 26, a car bomb exploded near a US-run civilian-military base in Kandahar city, but there were no casualties.