Philippine authorities are seeking to confirm reports that a lawmaker wanted by the international criminal court (ICC) secretly left the Senate premises where he had spent days evading arrest, an official said.

Presidential communications undersecretary Clare Castro told a press conference that authorities were trying to confirm the whereabouts of senator Ronald dela Rosa, after reports suggested he had slipped out of the heavily guarded building undetected before dawn.

“We are still getting official confirmation,” she told media, adding there had been no operations launched so far to arrest him.

Ronald dela Rosa, a senator who is wanted by the ICC for his role in overseeing former president Rodrigo Duterte’s “war on drugs”, avoided arrest earlier this week after he dramatically outran government agents and was offered protective custody by allies in the senate chamber.

Further chaos erupted in the senate on Wednesday night when gunshots were fired, forcing journalists to scramble for cover.

Dela Rosa had earlier said his arrest was imminent and called for supporters to gather outside the senate to protect him.

Philippines president Ferdinand Marcos later said no government personnel had been involved in the incident in the senate and there were no instructions to arrest Dela Rosa. He questioned whether the event was an attempt to “destabilise the government or trigger chaos”.

An investigation into the shooting is ongoing. Police said on Thursday they had detained a person in connection with the incident. Philippine police spokesperson Brigadier-General Randulf Tuano said the man was apprehended on the second floor of the senate building.

Interior secretary Juanito Victor Remulla had said senate security fired “warning shots” at several unknown armed men who had gone up the senate stairway.

Dela Rosa was head of the Philippine national police during Duterte’s administration and was a chief enforcer of anti-drugs crackdowns in which thousands of people were killed.

He is one of eight co-perpetrators named by the ICC in their case against Duterte, who is now detained at The Hague. An arrest warrant accuses him of “authorising, condoning and promoting” drug war killings, providing weapons, promising impunity and rewarding perpetrators, according to an ICC arrest warrant that was unsealed on Monday.

He did not respond to a request for comment, but has denied wrongdoing.

With Agence France-Presse