A suicide bomber set off explosives hidden under his jacket outside the entrance of Pakistan's navy headquarters Wednesday, killing one security guard and wounding 11 other people, police said.

The attack came hours after U.S. President Barack Obama warned that Pakistan and the United States "share a common enemy" in Islamic terrorists as he announced plans to send 30,000 more troops to Afghanistan. Pakistan's army has been fighting extremists in its northwestern frontier area and fears the U.S. surge will push more militants into its territory.

Wednesday's explosion occurred after the attacker, who appeared to be a teenager, was stopped as he approached the iron gates at the heavily fortified complex and was asked to remove his jacket, police said. Islamabad commissioner Fazil Asghar said the naval official who approached the youth was killed.

The suicide bomber was ordered to stop at the first security layer but did not stop, navy Capt. Mubeen Bajwa said, adding that five other navy officials and six civilians were wounded in the blast.

Security forces quickly cordoned off the area, and the naval installation suffered no damage because it was a safe distance from the gate.

Mohsin Aziz, 30, was stopped at a traffic light in his car at a nearby intersection when he said a young man wearing traditional Pakistani clothing with a black jacket and a white cap ran from a yellow van carrying two other people toward the naval complex gate.

The man ignored naval guard calls for him to stop, Aziz said, describing a grisly scene of blood, human remains and shattered glass.

While Pakistan has been hit by several suicide bombings in recent months, Wednesday's blast was the first in the capital since a double suicide bombing killed six people at the International Islamic University on Oct. 20. Militants also shot and killed a senior army officer and a soldier in a residential part of the capital in October.

On Tuesday, a teenage suicide bomber killed an anti-Taliban lawmaker in his house in Pakistan's Swat Valley, the site of a military offensive over the summer that was largely considered successful.

In mid-October, the army launched another major assault in the border region of South Waziristan that has reclaimed several towns.

Pakistan is under tremendous U.S. pressure to root out militants from the border area where they frequently attack American and Afghan troops.

Obama said Taliban sanctuaries based in Pakistan "cannot be tolerated" in his speech Tuesday to announce that the U.S. will send 30,000 more troops to Afghanistan.