Around 16 police vehicles and a truck were seen entering his residence in Kuala Lumpur, according to state-run news wire Bernama.
Najib, who unexpectedly lost last week's election, stands accused of embezzling hundreds of millions of dollars from the 1MDB state development fund. He denies the corruption allegations and was cleared in a government investigation.
Malaysian police cars enter the road leading to former Prime Minister Najib Razak's residence in Kuala Lumpur on May 16, 2018. Source: Mohd Rasfan / Getty Images
But his successor and former mentor, 92-year-old Mahathir Mohamad, instructed police to re-investigate the case and put Attorney-General Mohamed Apandi Ali on leave, over allegations he helped cover up the corruption scandal.
In a press conference on Thursday outside Najib's residence, the former premier's lawyer said no documents had been seized during the raids, just personal belongings.
Harpal Singh Grewal said Najib and his family "were cooperative" and that he believed the search had been carried out "under the money laundering act".
He also confirmed that police had simultaneously raided an apartment belonging to Najib.
Late Wednesday, Mahathir, who gained a reputation as an authoritarian ruler during a previous stint in power between 1981 and 2003, told reporters arrests would only be made when there was clear evidence of wrongdoing.
Former Malaysian prime minister Najib Razak has denied any wrongdoing. Source: AFP
Mahathir and Najib had a bitter falling-out two years ago over Najib's alleged involvement in the 4.5-billion-dollar 1MDB scandal and Mahathir made the allegations against his former protege a focus of his election campaign.
