Government security forces are on heightened alert ahead of former President Rodrigo Duterte's birthday which is seen to spur rallies and push for a non-remittance of overseas Filipino workers earnings from March 28 to April, according the National Security Council (NSC).

In an interview with reporters last Wednesday, NSC Assistant Director General Jonathan Malaya said they have yet to identify significant security threats but they are wary of any potential unrest during the event.

"We are monitoring closely the situation and as mentioned by our Armed Forces of the Philippines Vice Chief of Staff a while ago, we have yet to monitor a significant security threat with relation to what may happen on March 28," Malaya said.

Armed Forces of the Philippines (AFP) vice chief of staff Lt. Gen. Jimmy Larida said they are coordinating with the Philippine National Police (PNP) for Friday's events.

Calls are said to be growing from supporters of Duterte to bring him home so he can face the cases against him on the war on drugs of his administration, which claimed the lives of at least 6,000 people.

Duterte has been detained since March 11 in the Netherlands, where he will face the International Criminal Court (ICC) on alleged crimes against humanity. DMS