Singapore's leader criticised "malicious and baseless" claims in an article linking him to a corruption scandal, as he testified on Tuesday at the start of his defamation suit against a blogger. 

Prime Minister Lee Hsien Loong is suing Leong Sze Hian after the blogger shared an article on Facebook linking the premier to the money-laundering scandal at state fund 1MDB in neighbouring Malaysia.

Leaders in the tightly controlled city-state have frequently turned to the courts to take on critics -- ranging from political opponents to foreign media outlets -- in libel suits.

They argue legal action is necessary to protect their reputations but rights groups accuse the government of seeking to silence dissent.

Taking the stand at the start of the trial, Lee defended his decision to sue Leong, saying the allegations undermined the government's "integrity and honesty".

The article that Leong shared, originally published in a Malaysian news portal, alleged that Lee was the target of an investigation in Malaysia over the 1MDB state fund. 

Billions of dollars were looted from the investment vehicle in a scandal that involved Malaysia's former leader Najib Razak and his inner circle.

Lee, 68, also said he suffered damage to his own reputation.  

Leong's lawyer Lim Tean argued the libel suit was unnecessary as authorities had denied the allegations. 

He said the prime minister had "picked on the defendant when there are many others who shared the (defamatory) article".

The case will run until the end of the week.

On Friday, Lim, who is also an opposition politician, was arrested on suspicion of harassment and misappropriating money and claimed the move was politically motivated. Police denied his claim.

Singapore's leaders take a zero-tolerance approach towards corruption and are sensitive to allegations of graft.