The banker brother of Najib Razak has intervened in the financial scandal swirling around Malaysia and its prime minister, saying the future at home "terrifies" him.

Nazir Razak, chairman of CIMB, Malaysia's second-biggest bank, took to Instagram the day after Swiss authorities declared that there were "serious indications" that $4bn had gone astray in Malaysia.

"I just can't see how our institutions can recover, how our political atmosphere can become less toxic, how our international reputation can be repaired," he wrote on the social media site.

The fallout from corruption claims surrounding the 1MDB state investment fund, whose advisory board is chaired by Mr Najib, has triggered investigations in Switzerland, Singapore, the US and Hong Kong.

Mr Najib has admitted receiving $680m in his personal bank account, though he denies wrongdoing. The country's attorney-general said last week that the transfers to the prime minister were a donation from the Saudi royal family.