KANDAHAR – The commander of US and NATO forces in Afghanistan went on national television on Tuesday to apologise for a deadly airstrike, an extraordinary attempt to regain Afghans' trust while a mass offensive continues against the Taliban in the south. Two US Marine battalions, accompanied by Afghan troops, pushing from the north and south of the insurgent stronghold of Marjah finally linked up after more than a week, creating a direct route across the town that allows convoys to supply ammunition and reinforcements. In a video translated into the Afghan languages of Dari and Pashto and broadcast on Afghan television, a stern Gen. Stanley McChrystal apologised for the strike in central Uruzgan province that Afghan officials said killed at least 21 people. The video was also posted on a NATO website. "I pledge to strengthen our efforts to regain your trust to build a brighter future for all Afghans," McChrystal said in the video. "I have instituted a thorough investigation to prevent this from happening again." In another development, a remote-controlled bomb killed at least ten Afghan civilians and wounded 14 in front of a government building in southern Afghanistan yesterday, a government official said. The blast was in Lashkar Gah, capital of Helmand, Afghanistan's most violent province. NATO-led troops are in the 10th day of an operation to flush the Taliban out of nearby Marjah district, where the insurgents had set up their last big stronghold in Helmand. "The blast was caused by explosives attached to a bicycle and was controlled remotely," said Dawud Ahmadi, spokesman for Helmand's provincial government. He said later all the casualties were civilians. "The latest information we have said that seven people have been killed and 14 wounded," Ahmadi said. Violence across Afghanistan last year hit its highest levels since the Taliban were ousted by US-backed Afghan forces in late 2001. The insurgents have made a comeback and are resisting efforts by President Hamid Karzai's US-backed government to impose control. In Zabul province, also in the south, a roadside bomb hit a convoy of Romanian soldiers serving with the NATO-led International Security Assistance Force (ISAF) yesterday, said Mohamed Jan Rasoulyar, a spokesman for the provincial governor. Five casualties were evacuated from the site, Rasoulyar said, but it was not clear if anyone had been killed. Meanwhile, Afghan security forces have managed to arrest two senior members of the Taliban group in Afghanistan's southern province of Kandahar. "Two key Taliban commanders Mullah Ramazan and Mullah Sheikh who had led subversive activities in the western Herat province were detained in Kandahar on Sunday night," the spokesman for police in west Afghanistan Abdul Rauf Ahmadi told reporters yesterday.