All three leaders have been sharp critics of Najib, calling for his resignation following the allegations of graft and mismanagement at 1MDB.
Malaysia's central bank said on Thursday that it had issued a letter of administrative compound to 1MDB, a Malaysian state investment fund, for failing to fully comply with financial directions.
The Malaysian parliament's bipartisan Public Accounts Committee (PAC) has blamed the founding chief executive of 1Malaysia Development Berhad (1MDB) for the state investor's financial troubles which have rocked market confidence in the country and fuelled calls for Prime Minister Najib Razak's resignation.
Monetary Authority of Singapore ( MAS) said on Wednesday it is in contact with financial institutions in relation to Malaysia's probe into allegations that hundreds of millions of dollars had been transferred to accounts of Prime Minister Najib Razak.