Nigeria army frees more hostages, extends offensive

*17 foreign hostages, 4 Nigerians so far rescued

*One militant killed as offensive extends to Rivers state

Military vow to push on until missing soldiers found

By Segun Owen

WARRI, Nigeria, May 24 (Reuters) - Nigerian security forces freed three more Filipino hostages on Sunday and extended their offensive against militants to Rivers state where one rebel leader was shot dead, an army spokesman said.

The military began its biggest onslaught for years over a week ago, bombarding militant camps around the oil-city of Warri in Delta state from the air and sea before sending hundreds of soldiers to hunt down rebels believed to have fled into surrounding communities.

Helicopters and planes were used to survey the creeks and guide ground troops to try and flush out militants from remote communities around the port of Warri, a military spokesman said.

"A cordon and search operation ... has led to the rescue of additional three Filipinos," Colonel Rabe Abubakar, spokesman of the joint taskforce overseeing security in the delta, said.