The blogger had shared the post on his Facebook page on November 7, 2018, which contained a link to an article by Malaysian news site The Coverage, reports The Straits Times.

The article contained allegations that then Malaysian Prime Minister Najib Razak had signed "secret deals" with Lee in exchange for Singapore banks' help in laundering money from the scandal-ridden 1Malaysia Development Berhad (1MDB) fund.

The four-day hearing is taking place at the city-state's High Court.

Lee is being represented by his lawyer Davinder Singh and Leong's advocate Lim Tean is also an opposition politician who heads the Peoples Voice party.

As the Prime Minister took the witness stand, Lim repeatedly questioned him on why he chose to sue only Leong and not "thousands" of others who shared the offending article, reports Channel News Asia.

He also asked whether the government's actions in debunking the false allegations in the article were enough, and questioned if Lee had to take the step to sue Leong.

In reply Lee said: "When an accusation is made against me as Prime Minister, which is a serious allegation in this case, the government has to take it very seriously. I have to take it very seriously as Prime Minister, as head of the Government and also as me... to protect my own reputation and standing."

The courtroom was packed on Tuesday, subject to safe-distancing guidelines, with tickets to the public gallery running out hours before the hearing began.