Malaysian police have arrested three opposition politicians and activists and charged another with sedition, launching a crackdown on dissent three weeks after a divisive election that sparked a series of protests.

Opposition member of parliament Tian Chua, who is vice president of the opposition Pakatan Rakyat (People's Alliance), and pro-opposition activists Haris Ibrahim and Tamrin Ghafar, were arrested on Thursday for offences under the Sedition Act, Kuala Lumpur police chief Mohamed Salleh said.

Tian said on his Twitter page that he had been picked up by police as he was about to board a flight at Kuala Lumpur's budget air terminal.

Police also raided the offices of three opposition newspapers, and seized hundreds of copies of their publications for suspected infringement of regulations, the interior ministry said in a statement.

"The recent arrests are a matter for the police, who are acting to uphold the law," a government spokesman said. "The detentions came after the police received numerous reports against the defendants by members of the public."

Earlier, Adam Adli Halim, 24, was charged under the Sedition Act over a statement made at a public post-election forum on May 13. He had been held in custody for five days until he was released on bail on Thursday, his lawyer Fadiah Nadwa Fikri said.

Adam Adli apparently called for people to "go down to the streets to seize back our power" while addressing the forum.

The student, who became publicly known in 2011 when he brought down a flag with Prime Minister Najib Razak's portrait at the ruling party's headquarters during a demonstration, faces three years in prison and a fine if convicted.

Disputed election

Opposition activists have staged numerous peaceful demonstrations since the May 5 general elections, which the National Front coalition won with a weakened parliamentary majority.

They insist the coalition, which has governed since 1957, retained power through bogus ballots and other irregularities, but Najib and electoral authorities deny manipulating the results.

The Sedition Act is widely criticised as a method of oppressing democratic dissent, to the extent that the prime minister pledged last year to repeal it.

Conservatives in the United Malays National Organisation (UMNO), the main party in the ruling coalition, have urged Najib, who faces a possible leadership battle within months, to take a firm line against "dissent".

Malaysian activists and the opposition have dismissed Najib's moves to amend a series of security laws to guarantee greater civil liberties as window-dressing to appease voters.

Adam Adli's lawyer heavily criticised the use of the act against his client.

"It's clearly still being used to stifle dissent," Fadiah told the AFP news agency. "The law is open to abuse ... it's an infringement to freedom of speech and freedom of assembly."

Human rights group Amnesty International has also gone on record as being against the law.

"The Malaysian authorities must ensure that peaceful political dissent is protected both in law and practice," it said in a statement on Wednesday.