Kabul, (Agencies): A suicide bomber blew himself up at the entrance to a government office on Monday in northern Afghanistan, killing at least 31 people, police said.

The attack occurred around noon in Imam Sahib district of Kunduz province, said district police chief Abdul Qayum Ebrahimi. He said the district police and a government office that distributes official identification papers are both located in the building that was hit by the explosion.

There has been sharp slide in security in recent months in Kunduz and other northern provinces, where there are known hide-outs for the Taliban, al-Qaida and fighters from other militant factions, including the Haqqani network, Hizb-i-Islami and the Islamic Movement of Uzbekistan.

NATO has sent more troops to the north and has been pushing harder into militant-held areas.

Earlier this month, a bomber killed the district chief of Chahar Dara in Kunduz province.