Jakarta. Activists are demanding police investigate a non-fatal shooting at a union headquarters in East Jakarta on Tuesday.

"We're pressing the police to investigate this incident immediately and arrest the perpetrators," Mudhofir Khamid, president of the Indonesian Confederation of Prosperous Labor Unions (KSBSI), said on Wednesday.

Mudhofir said he believed the shooting, which occurred about 10:45 p.m. and did not injure anybody, was an act of terror designed to intimidate workers ahead of Labor Day demonstrations on May 1.

"The sound of gunshots took us all by complete surprise. At first, we thought it was some passerby throwing firecrackers," said Mudhofir, who was in a meeting with several labor union leaders at the time.

Several cars parked in front of the office were damaged by the gunfire.

The incident was immediately reported to Jatinegara Police.

Jumhur Hidayat, chair of the Federation of Indonesian Maritime Workers (FSPMI), condemned the attack, and agreed it may have been related to the planned upcoming May Day demonstrations.

"This is terror against the workers and the shootings remind us of New Order-era repression," Jumhur said. "But the labor movement will not be cowed by such a cowardly act."