KUNDUZ (Agencies) - A suicide bomber killed at least 31 people in a government office in northern Afghanistan on Monday, officials said, with violence spiralling across the country even before an expected spring offensive. In Kunduz province in the north, the centre of a growing front in the Taliban-led insurgency, a suicide bomber killed at least 31 people, Mohammad Ayoub Haqyar, the chief of Emam Saheb district, said. Another 40 were wounded. Haqyar said the bomber struck while people were queuing to collect identity cards inside a government office. Kunduz police chief, Abdul Qayum Ibrahimi, said three police were among the dead and that many civilians were wounded. A local man, Mohammad Ismail, described the scene in the hospital where the wounded were being treated as chaotic.