A bomb blast at the main gate of a hospital in a lawless tribal area of northwest Pakistan killed at least four people and wounded four others on Saturday, officials said.
The explosion took place in Khar, the main town of Bajaur tribal district bordering Afghanistan where the military has carried out several offensives against Al-Qaeda-linked Taliban militants.
"At least four people were killed and four others were wounded in the blast outside the main gate of the hospital," Mohammad Riaz, chief doctor at the government hospital, told AFP.
Local administration official Abdul Haseeb confirmed the bombing and casualties and said it was not immediately clear if the bomb was detonated remotely or was a suicide attack.
"It appears to be a suicide attack but I cannot confirm right now," he said.
Bajaur is one of seven districts that make up Pakistan's Federally Administered Tribal Areas (FATA). The semi-autonomous region of mountains, valleys and caves is one of the most deprived and ill-educated in the country.
It has been a stronghold for Afghan Taliban, Al-Qaeda and other Pakistani militant groups, and a battleground between the army and insurgents.
Pakistan has lost more than 3,000 soldiers in the fight against homegrown insurgents but has resisted US pressure to do more to eliminate havens used by those fighting the Americans in Afghanistan.