A leading Malaysian opposition politician and vocal critic of Prime Minister Najib Razak went on trial for corruption Monday as elections loom, in a case critics say is politically motivated.

Lim Guan Eng, who has repeatedly demanded that Najib explain a massive financial scandal that has engulfed his administration, appeared in the High Court in the northern state of Penang.

Supporters gathered outside the court, shouting “Support Guan Eng” and “Arrest Najib”, as Lim denied two counts of abuse of office at the start of the trial.