A suicide car bomber struck a military truck in northwestern Pakistan, killing at least 20 people just days after troops were sent to the lawless region to quell pro-Taliban militants.
The blast came a week after the bloody assassination attempt in the southern city of Karachi on ex-Prime Minister Benazir Bhutto, who plans to start traveling elsewhere in Pakistan on Saturday.
Thursday's attack underlined the worsening security situation in the country, particularly in the conservative tribal region near the border with Afghanistan where militants linked to the Taliban and al-Qaida increasingly hold sway. The rise of militancy in the region has shaken the authority of President Gen. Pervez Musharraf, a key US ally in its war on terror.
The bomber hit a truck carrying about 45 Frontier Constabulary forces near the main police station in Swat district, where 2,500 paramilitary troops were deployed this week to counter a militant cleric. The blast tipped the truck on its side and detonated ammunition inside.