Three police cars were damaged in a provocative incident by alleged supporters of a political party, at Sekolah Kebangsaan (SK) Bukit Indera Muda, here last night.

Penang police chief, Datuk Abdul Rahim Hanafi said the incident occurred when a Bomb Disposal Unit of the Royal Malaysia Police (PDRM) and a police team were carrying out inspection to prevent any undesired incident on polling day for the Permatang Pauh Parliamentary by-election, today.

"The provocative act should not have occurred because everyone already knew the SOP (standard operating procedure) of the police in carrying out checks at all the polling centres before polling day.

"During the incident, a group from the Bomb Disposal Unit were carrying out a flushing exercise and inspection to ensure that the polling centres were safe for use.

"They (the party supporters) had encircled the area, closed the school gate and damaged the police cars," he told reporters after visiting the polling centre at Sekolah Menengah Kebangsaan (SMK) Guar Perahu, here today.

Abdul Rahim said no one was injured during the incident as the police managed to control the situation by discussing with several leaders of the political party who were at the location.

He said police opened three investigation papers on the incident under the Penal Code for firstly obstructing civil servants from discharging their duty, rioting and causing mischief.

"Besides SK Bukit Indera Muda, two other polling centres were also disturbed by the group in the incident yesterday but police managed to control the situation," he said.

He called on party supporters to refrain from provoking the police as they were only carrying out their task to maintain peace and public order at the polling centres.

"The party supporters created provocation so that the police would take action on them which could result in chaos. However, we took the negotiation approach to calm down the situation," he said.

In the incident last night, a police team from the Bomb Disposal Unit were surrounded by at least 300 supporters of a political party in front of the school gate.

It is learnt that the party supporters had obstructed the school's exit by parking their cars opposite the gate, trapping the policemen in the school compound.

Meanwhile, Abdul Rahim said 112 police reports for election offences had been received since nomination day on April 25 until early today and police had opened 12 investigation papers.

"As at 10.30 am, the polling process had been smooth and I had also directed policemen on duty to separate the position of the supporters of the (contesting) political parties at the polling centres to avoid provocation between them," he said.

The Permatang Pauh Parliamentary by-election involves a four-cornered contest between Suhaimi Sabudin (Barisan Nasional candidate), Datuk Seri Dr Wan Azizah Wan Ismail (Parti Keadilan Rakyat), Azman Shah Othman (Parti Rakyat Malaysia) and Salleh Isahak (Independent).

The by-election is being held as the incumbent, Datuk Seri Anwar Ibrahim had lost his eligibility as an elected representative after his conviction for sodomy and is now serving a five-year jail term.