KANDAHAR (Reuters/AFP) - Suicide bombers killed at least seven people on Sunday when they attacked a police convoy in Afghanistans southern province of Helmand, the Interior Ministry said. Despite reinforcements to foreign forces, violence has surged to its worst level in the past year, the bloodiest period since US-led troops overthrew the Taliban govt more than seven years ago. In the latest incident, two suicide bombers riding on motorcyles blew themselves up near a group of police who had just parked their vehicles in the Girishk district of Helmand, said Assadullah Sherzad, provincial police chief. In Kabul, the Interior Ministry said seven people, including two police, two soldiers and three civilians, were killed. Another 20 people, 10 of them civilians were wounded, it said. The Ministrys spokesman, Zemarai Bashary had earlier told AFP that nine people including four police, four civilians and an army soldier had died in the blasts. The statement said the first bomber riding a motorbike detonated near the police patrol. The second bomber wearing explosives on his body detonated 20 minutes later as security forces gathered there in response, it added. The Taliban claimed responsibility for the twin bombing. We, the Taliban carried out the attacks. It was carried out by one of our loyalists, Yousuf Ahmadi, a Taliban spokesman told AFP from an undisclosed location. Meanwhile, 11 Afghan construction workers were killed in separate bomb blasts similar to those carried out by Taliban insurgents in violence-plagued Afghanistan, authorities said. In one attack, a bomb blew up a construction company vehicle in a remote eastern district on the border with Pakistan, killing eight workers, the Interior Ministry said. Police in Nangarhar province had said earlier that seven had died in the attack in the Haska Mina district. They were Afghan civilians working as roadworkers, engineers and supervisors for a company doing various construction work in the district, provincial police spokesman Abdul Ghafoor told AFP. Another bomb exploded Sunday in the southern province of Zabul, killing three more construction workers, the Interior Ministry said in a separate statement.