A suicide bomber blew himself up Thursday in southern Afghanistan, killing one Afghan intelligence service officer and wounding more than two dozen other people.

As tens of thousands of U.S., Afghan and coalition troops push to seize control of Taliban strongholds in the south, insurgents have stepped up their attacks on individuals aligned with pro-government forces.

In Thursday's violence, intelligence officers acting on suspicions stopped a car in the Spin Boldak district of Kandahar province, said Lutfullah Mashal, a spokesman for the Afghan intelligence service in Kabul.

Intelligence officers killed one bomber in the car, Mashal said. Another bomber, who had been shot, got out of the car, fell to the ground and acted as if he was dead, he said.

When the intelligence officers walked toward him, he detonated his vest full of explosives, Mashal said.

The provincial governor's office reported that 26 people were wounded — 18 civilians, two Afghan border policemen and six intelligence officers.

In the east, a cleric died Thursday in a powerful explosion inside a religious school east of Khost city, according to Gen. Abdul Hakim Isaqzai, police chief in Khost province. He said police were investigating whether someone planted a bomb in the school or if someone was making one.