A suicide bomb killed 35 people near Pakistan’s military headquarters Monday and a second blast wounded several police, continuing a wave of terrorism that prompted the United Nations to suspend long-term development work near the Afghan border.

The rash of attacks by Islamist militants has killed at least 300 people across Pakistan over the past month - including 11 U.N. workers - and threatened to destabilize the nuclear-armed nation.

The violence has grown bloodier since the government launched an anti-Taliban offensive in mid-October, pushing into the impoverished and underdeveloped tribal region of South Waziristan.

U.S. military, intelligence and diplomatic officials increasingly are concerned by the attacks in and around the Pakistani capital of Islamabad and in the country’s ...