A suicide bomber rammed an explosives-laden vehicle into a military checkpoint in Pakistan's troubled northwest on Saturday, killing at least 20 people, officials said. While terror attacks are spreading across Pakistan, the onslaught remains fiercest near Taliban strongholds along the Afghan border, where al-Qaida fugitives - perhaps including Osama bin Laden - have found sanctuary. The explosion demolished the checkpoint and severely damaged an adjacent building housing troops and police, said Farid Khan, a senior police official in the nearby town of Hangu. At least 18 members of the security forces as well as two civilians died, Khan said. More than a dozen other people were wounded, including the local police chief, other officials said.