Islamabad, Pakistan (CNN) -- Five people were killed overnight when Pakistani security forces hunting for militants involved in a deadly attack earlier this week raided a hospital in the country's volatile tribal region and battled militants there, two Pakistani intelligence officials said Thursday.
The eight hours of fighting took place at Hafiz Medical Center in the South Waziristan town of Wana, beginning at 11 p.m. Wednesday. A Sudanese man, three men from unidentified Arab countries and a woman of unknown nationality were killed, the officials said.
It is not known whether the men were foreign militant fighters.
The raid follows an insurgent attack on a Pakistani security force checkpoint Monday, which left two security personnel dead and two others injured. Several militants were injured in the firefight, and some ran away.
Authorities said militants at the hospital put up a strong fight. After the attack, 18 militants were arrested.