Malaysia's former prime minister Najib Razak (C) walks after Friday prayers at the Barisan Nasional party headquarters in Kuala Lumpur on May 18, 2018. (Photo: VCG)

Former Malaysian Prime Minister Najib Razak was arrested by anti-corruption investigators Tuesday, officials said, the latest dramatic development in a widening graft probe that has engulfed the ex-leader.

Najib will be charged Wednesday, a taskforce set up to investigate corruption involving Malaysian state fund 1MDB said in a statement.

"1MDB's Task Force confirmed the arrest of Datuk Seri Mohd. Najib Tun Razak," it said.

It said the arrest "was made at his home" in the upmarket Jalan Langgak Duta district in Kuala Lumpur.

He will be "charged on July 4, 2018 at 8:30 am at the Kuala Lumpur Court," it added.

Earlier, a security source said that agents from the Malaysian Anti-Corruption Commission arrested Najib.

"They came in three to four unmarked cars," the source, a senior security official familiar with the arrest, told AFP.