Berliner Tageblatt - Shots heard at Philippine Senate as lawmaker wanted by ICC holds out: AFP

At least five shots rang out, sending journalists, lawmakers and staff fleeing for cover, minutes after soldiers with rifles and protective gear went up the stairs of the legislative building, the journalists said.

The dramatic scenes unfolded as Senator Ronald Dela Rosa -- former president Rodrigo Duterte's top enforcer during his bloody drug war -- remained holed up in the Senate complex to dodge arrest and transfer to the Netherlands over alleged crimes against humanity.

His current whereabouts after the shooting were not immediately known.

Earlier Wednesday, Dela Rosa had appealed to the military to oppose attempts to detain him, urging former colleagues to resist any move by President Ferdinand Marcos's government to hand him over.

"My fellow men in uniform" should "express their sentiment" that the government "should not hand me over to foreigners", he said.

Senate President Alan Peter Cayetano, who had barred government agents from arresting his ally, said on his official Facebook page he did not know who fired the shots.

"We heard gunshots and we don't know what is happening. Everyone's locked in their rooms now. We cannot go out, we cannot secure our other staff," he added.

"Why are we under attack here? ... Please help us."

A television journalist was seen crying as she reported live from inside the building, while another senator, Robin Padilla, urged reporters to evacuate.

Dela Rosa, known as "Bato", served as national police chief from 2016 to 2018 during the early phase of Duterte's anti-drug campaign.

The crackdown left thousands dead, human rights monitors say, many of them drug users and low-level narcotics peddlers.

Duterte was arrested in March last year, flown to the Netherlands on the same day, and is detained in the Hague where he awaits trial.

Dela Rosa had not been seen publicly since November before emerging on Monday to take part in an unexpected vote that helped Duterte loyalists capture control of the Senate.

C.Kovalenko--BTB