FELDA SAHABAT, Malaysia (Reuters) - Malaysian Prime Minister Najib Razak said on Thursday that Philippine militants being tracked after the military launched an assault against them in Sabah state must surrender unconditionally, rejecting the group's offer of a ceasefire.

Asked how long the operations to track down the remaining gunmen would continue, Najib told reporters in Sabah: "For as long as it takes to eliminate them."

At least 27 people have died in clashes since Tuesday's military assault, about a month after the militants entered Sabah to press an ancient claim to the state from a sultanate in the southern Philippines.

(Reporting by Angie Teo; Writing by Stuart Grudgings; Editing by Ron Popeski)