Malaysia has frozen hundreds of bank accounts believed linked to sovereign wealth fund 1MDB, officials said Monday, as they stepped up an anti-graft probe that could engulf former Prime Minister Najib Razak.

A special government task force investigating a corruption scandal involving 1MDB said it froze 408 bank accounts containing a total of 1.1 billion ringgit ($272 million) last week.

"The accounts are believed to be connected with the misappropriation and misuse of 1MDB funds," the task force said in a statement.

"They involved nearly 900 transactions made between March 2011 and September 2015."

The funds in the frozen accounts came from individuals, political parties and non-government organizations, it said without mentioning names.

However, the task force's statement followed local media reports last week that accounts belonging to Najib's political party, the once-powerful United Malays National Organization (UMNO), had been frozen.

Najib resigned as the party's leader days after his UMNO-dominated Barisan Nasional coalition -- which ruled Malaysia for more than 60 years -- was roundly defeated in the May 9 elections.

Najib is being investigated over allegations that billions of dollars were looted from 1MDB, a state fund he founded.

Both Najib and the fund deny any wrongdoing.

Premises linked to the former prime minister and his family were raided recently by the police, who uncovered a treasure trove of cash and valuables said to be worth up to 1.1 billion ringgit.

The items included luxury handbags believed accumulated by his wife Rosmah, who has been widely criticized for her extravagant shopping sprees.

However, no charges have been filed against them so far.

Najib has said most of the items seized were gifts from friends and foreign dignitaries, including royalty, during special occasions such as official visits and birthdays.

Local media, meanwhile, said that Najib's stepson Riza Aziz, an aspiring Hollywood producer, is expected to be questioned by anti-graft officials on Tuesday.