FILE PHOTO: Philippine President Rodrigo Duterte delivers his State of the Nation address at the House of Representatives in Quezon city, Metro Manila, Philippines July 23, 2018. REUTERS/Czar Dancel

MANILA (Reuters) - Philippine President Rodrigo Duterte said on Friday he might send the navy’s most modern frigate to waters off Libya in a bid to “save” three Filipinos and a South Korean kidnapped last month from a water plant in the north African country.

South Korea has redirected a vessel taking part in anti-piracy operations in the Gulf of Aden to help in the release of the four men taken almost a month ago, according to news agency Yonhap.

Duterte said he might do the same and would raise the issue next week at a regular meeting of his top military and police commanders.

“If they start hurting those three Filipinos, I will bring a frigate there, I am not kidding,” he said in a speech.

The men were taken near Ishwirif by an unknown armed group.

Video footage appeared on social media this week of the four men confirming their names and nationalities and appealing to their presidents for help.

Various armed groups, including Islamist militants linked to al Qaeda and Islamic State, have a presence in Libya. Risks for foreign workers have been high due to insecurity in much of the country in the years following a 2011 uprising.