Former prime minister Najib Razak is expected to be charged today in connection with the RM2.6 billion (S$860 million) said to be-long to scandal-plagued state fund 1Malaysia Development Berhad (1MDB) that was found in his personal bank accounts.

He was arrested yesterday after he was asked to report to the Malaysian Anti-Corruption Commission (MACC) headquarters, and was to spend the night in lock-up.

An MACC statement yesterday said: "The MACC will assist the Royal Malaysia Police in recording Mohd Najib's statement in its probe under the Anti-Money Laundering, Anti-Terrorism Financing and Proceeds of Unlawful Activities Act 2001 before he is brought to court tomorrow at 3pm."

Najib already faces seven charges - three counts of criminal breach of trust (CBT), one count of abuse of power and three counts of money laundering - all relating to RM42 million belonging to SRC International, an energy company and former 1MDB subsidiary.

The money was allegedly transferred from SRC International to his personal bank accounts.

The case against Najib began in July, when he was charged with CBT and abuse of power involving a total of RM42 million which was entrusted to him between December 2014 and March 2015, when he acted as SRC's adviser.

He was prime minister and finance minister at the time. SRC was placed under the jurisdiction of the Finance Ministry in 2012.

Last month, he was hit with three counts of money laundering charges involving the same funds.

The 65-year-old has pleaded not guilty to all seven charges, which he claims are politically motivated. He has posted bail of RM1 million.

Najib is the first Malaysian prime minister to face criminal charges after years of being dogged by the multibillion-dollar 1MDB scandal.