Malaysia's former finance minister Lim Guan Eng was arrested by the anti-graft body last night, following weeks of a probe into a RM6.3 billion (S$2.1 billion) undersea tunnel project green-lit during his tenure as Penang chief minister.

Mr Lim was arrested shortly after he arrived at the Malaysian Anti-Corruption Commission (MACC) headquarters for questioning.

Mr Lim, 59, who is also the secretary-general of the Democratic Action Party, which has the most seats in the Malaysian Parliament, will face two charges relating to the undersea tunnel. He will also be charged with another offence at a Penang sessions court next week, the MACC said in a statement.

According to the commission, Mr Lim will be charged with bribery and abuse of power relating to the tunnel project, and a separate abuse of power charge over the additional unspecified case.

If found guilty, he could face up to 20 years in prison on each charge.

MACC has been investigating the undersea tunnel project for close to three years, but the probe seemed to fizzle out after a series of arrests of businessmen and officials connected to the project in 2018.

But it appeared to gather momentum again after the collapse of the Pakatan Harapan (PH) government, in which Mr Lim was finance minister, earlier this year.

The commission questioned several prominent Penang politicians in recent weeks to aid its probe, including Mr Lim's successor as Chief Minister, Mr Chow Kon Yeow.

Mr Lim earlier faced corruption charges over the purchase of a bungalow below the market price in 2016, but they were controversially dropped in 2018 by then Attorney-General Tommy Thomas, months after PH won federal power.

De facto Law Minister Takiyuddin Hassan recently said the MACC could relaunch its probe into Mr Lim's bungalow purchase.

Mr Lim was Penang's chief minister between 2008 and 2018, and early studies for the tunnel started during his administration in 2016. The ambitious tunnel project is not due to be completed until 2025.