More than 170,000 people have signed onto a Facebook protest calling for Malaysian Prime Minister Najib Razak to resign after a violent police crackdown on peaceful pro-democracy protesters on the weekend.

The "100,000 People Request Najib Tun Razak Resignation" had smashed its target less than four days after it was set up on Saturday as riot police crushed the demonstration in the capital Kuala Lumpur.

More than 1,600 people were arrested in the biggest street protest the Southeast Asian state had seen in years, prompting condemnation from human rights groups such as Amnesty International.

It was organized by opposition parties and reform group Bersih 2.0, which has demanded a royal probe into the electoral system.

The country's election rules heavily favor Najib's Barisan Nasional coalition, which has ruled Malaysia for half a century.

The coalition has come under mounting pressure for reform ahead of elections widely expected next year, after its majority was cut in the previous general election three years ago.

AFP news agency reported that the Facebook page had initially attracted around 300 "likes" per minute.

It reached its 100,000 target early Monday and showed 172,868 "likes" on Wednesday morning.

"I don't understand why the harshness, the beatings (by police) and the tear gas," according to a post by supporter Sofie Muhammad.

"The crowd didn't even throw stones at the shops, why is the government afraid? All we want is free elections."

Amnesty International deputy Asia-Pacific director Donna Guest said Najib’s government "rode roughshod over thousands of Malaysians exercising their right to peaceful protest."

"This violent repression by the Royal Malaysian Police flies in the face of international human rights standards, and cannot be allowed to continue," she said in a statement released earlier this week.

"Any future peaceful demonstrations should be permitted and respected by the authorities."