KUNDUZ, Afghanistan (Reuters) - A suicide attack on an army recruitment center in northern Afghanistan killed 37 people on Monday, the third major assault in the area in less than a month, the deputy governor said.

Taliban spokesman Zabihullah Mujahid claimed responsibility for the attack on behalf of the militant Islamist group. Dozens more were wounded, officials said.

A Reuters witness heard gunfire in the area after the attack but Hamdullah Danishi, deputy governor of Kunduz province, said the casualties were all caused by a single suicide bomber.

"The death toll includes new recruits, army soldiers and civilians," Danishi told Reuters. A doctor in the Kunduz provincial hospital said 33 bodies had been brought in.

Violence is spreading fast in the once relatively peaceful north, with Kunduz a particular focus for insurgents.

The Kunduz police chief was killed by a suicide bomber while out on patrol in the city last week. In late February, another suicide bomber killed at least 30 people in a government office while people were queueing to collect identity cards in the Emam Saheb district of Kunduz.

The previous governor of Kunduz was killed in an attack on a mosque where he was worshipping last October.

The province has become established as an insurgent base over the past two years, with attacks radiating out into surrounding provinces while NATO-led International Security Assistance Force (ISAF) offensives have been concentrated in Taliban strongholds in the south and east.

ISAF said on Monday they had heard reports of the latest attack in Kunduz and were investigating.

In 2010, violence across Afghanistan hit its worst levels since the Taliban were ousted by U.S.-backed Afghan forces in late 2001, despite the presence of about 150,000 foreign troops. It has been rising this year even before an expected spring offensive against insurgents.

(Reporting by Fraidoon Elham and Hamid Shalizi, writing by Emma Graham-Harrison, editing by Paul Tait)

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