Najib arrived in Kelantan, which has the biggest problems among eight affected states, following his return from Hawaii on Friday after public criticism he had been absent as flooding worsened.
On Saturday, Najib announced an additional 500 million ringgit ($143.31 million) will be spent to aid victims after the flood subsides, following an initial government allocation of 50 million ringgit two days ago.
The number of people evacuated topped 160,000 at 0700GMT Saturday, according to the New Straits Times newspaper, a sharp increase from 100,000 a day before.
The prime minister attended briefings with the National Security Council, the National Disaster Management and Relief Committee, state government and local emergency responders, a statement on Friday said.
Northeastern peninsular Malaysia, which is worst affected part of the country, is regularly hit by flooding during the annual "northeast monsoon", but this year's rains have been particularly heavy.
Meanwhile, New Years celebrations have been canceled in Perak and Putrajaya city, Malaysia’s federal administrative center south of capital Kuala Lumpur.
The cancelation of programs in Putrajaya was announced by the federal territories minister, who defended Prime Minister Najib Razak against criticism for being abroad as the country deals with the worst floods in four decades.
"Some say PM does not bother, ministers don't bother... all this is propaganda and slander," the Insider quoted Tengku Adnan Tengku Mansor as saying at a press conference at the ministry's Christmas open house Thursday.
Explaining the costs of the New Year's Eve festivities were covered by the Ambank Group, he said he would consult the group’s chairman on whether the RM3 million ($850,000) for the celebration could instead be used in flood relief efforts.
Deputy Prime Minister Muhyiddin Yassin traveled to Kelantan Friday morning amid criticisms of the premier, national news agency Bernama reported.
While Kuala Lumpur has not been hard hit by flooding, Mayor Ahamd Phesal Talib has announced that the City Hall rescue unit, Fire and Rescue Department and other government agencies are ready to assist the public in the case of a natural disaster.
"We have enough personnel to face the flood situation. We will utilize the assets we have in the best way possible to provide immediate help to the flood victims," he told Bernama.
On Tuesday, nearly 100 people – including around 60 tourists – were stranded at a national park in Pahang that recorded its highest rainfall since 1971, and later rescued by helicopters and boats.
The tropical Southeast Asian nation, particularly Malaysia’s peninsular northeast, experiences flooding-related incidents during the Northeast Monsoon season every year.