Ammon News - Police said Thursday they detained a person in connection with gunfire the previous night inside the Philippine senate, where a lawmaker wanted by the International Criminal Court took refuge.

The shooting did not result in any casualties and came as the one-time enforcer of ex-president Rodrigo Duterte's deadly drug crackdown sheltered at the legislature.

It was not immediately clear how many suspects were involved in the shooting, with Philippine authorities saying investigation was ongoing.

"He (suspect) was arrested at the area of the incident, at the second floor of the senate building," Philippine police spokesman Brigadier-General Randulf Tuano told reporters.

Police seized live ammunition from the man, who was being tested for gunshot residue.

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

The gunmen later fired into the air and left, he added, while senators, including the fugitive Dela Rosa, barricaded themselves inside their offices.

Senator Ronald Dela Rosa took refuge in the senate aiming to avoid arrest on a warrant from the ICC for the crime against humanity of murder.

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, many of them drug users and low-level narcotics peddlers, according to human rights monitors.

His boss Duterte was arrested in March last year, flown to the Netherlands on the same day, and is detained in The Hague awaiting trial.

AFP