Opposition leaders today called for an investigation into the shooting of two protesters at a political rally which went ugly after police halted the event from proceeding.

Police, who also used tear gas and water cannon when a riot broke out at the rally in Terengganu on Saturday, have defended the action by a plainclothes officer who they said acted in self-defence.

Two PAS members were injured in the incident, with a 37-year-old man wounded in the lungs and a 21-year-old in the neck, but both are now in stable condition, the party said.

The leader of the PAS in Terengganu, Mustafa Ali, called on the government to hold a royal commission into the shooting. [Watch 3-min video]

"People recognised that the policeman in plain clothes was trying to instigate the violence. So they tried to catch him," he told a press conference.

"It has been planned. It was a collaboration between Umno and police. And it happened due to provocation. I call on the government to investigate the matter."

Other political parties and rights groups also hit out at the ruling party and police.

"What frightened me the most was the use of bullets to disperse the crowd who came to attend a peaceful gathering," said Abdul Khalid Ibrahim, secretary-general of the opposition PKR.

"It is not a good sign for democracy," he said. "I hope this is not an attempt by the government to silence the opposition. Such attitudes will make Malaysia less attractive to foreign investment."

Police: Both sides are investigated

Mustafa said the government was attempting to sideline PAS, which lost control of Terengganu to Prime Minister Abdullah Ahmad Badawi's ruling Umno party in 2004 elections.

"We are optimistic of regaining Terengganu so they are trying to stop our influence. They do not want our message to get across," he said.

Terengganu police chief Ayub Yaakob said that both the police officer and the 37-year-old victim were under investigation for attempted murder.

"Both sides are being investigated. We want to know what really happened," he said, insisting however that the officer had not intended to wound anyone.

"He was with the protestors when they turned on him. They started beating him. He fell down and in self-defence drew his gun and fired a warning shot into the air," he said.

"Unfortunately, two people were shot. I want it to be clear that we did not use a gun to disperse the crowd."