Reuters reported that witnesses saw around a dozen armed police enter Najib's home after he returned from prayers at a mosque.
A police spokeswoman could not be contacted for comment.
More than 100 people, including journalists and members of the public, gathered outside his family home after police vehicles arrived. The events were being streamed live on Facebook by local media and one account had attracted almost 8,000 viewers.
But the 92-year-old Mahathir, now himself arrayed against the BN coalition he once headed, led Anwar's pro-reform alliance to a stunning election victory last week and orchestrated the release of his old foe in an extraordinary rapprochement.
Mahathir Mohamad reacts as he speaks during a press conference at a hotel in Kuala Lumpur, Malaysia, on May 10, 2018. He has also ordered the attorney general who cleared Najib of any wrongdoing in 2016 to go on leave pending an investigation, while the head of the anti-graft body has resigned.
Milwaukee Bucks: Mike Budenholzer agrees to be next head coach, per reports
The New York Knicks and Phoenix Suns also met with the former Hawks coach, before agreeing to terms with their new head coaches. Kidd had been surrounded in scrutiny started with the moment he took over as coach of the Bucks.
Anwar's freedom is expected to ease fears of a growing rift within the newly formed coalition government, after differences erupted between supporters of Mahathir and Anwar over cabinet positions and Anwar's role in the party.
Mahathir pledged to hold Najib accountable. However, the relationship between the two remains volatile, and will largely determine what course Malaysia will chart in the coming months. As for his political future, he said he wants to take time to be with his family and that at least for now, he doesn't need to serve in cabinet. "We have enjoyed good relations with Malaysia under former Prime Minister Najib Razak, and cooperated on major projects that benefit both sides", Lee said.
"Anwar bin Ibrahim", said a statement issued by the palace.
"Seeing him walk free makes me emotional, but the fight is not over", said Ridzuan Ismail, an Anwar supporter at the hospital.
Anwar was Mahathir's deputy in the 1990s, but fell out with his mentor during the 1997-99 Asian financial crisis.
South Sudan on alert as Ebola outbreak reported in Congo
It's the ninth Ebola outbreak in the DRC since the virus was first discovered there in 1976, when the country was named Zaire. But, since the 2014-16 outbreak, other countries have had Ebola outbreaks , which many people may not have heard about.
Sodomy is illegal in Muslim-majority Malaysia, where the offence carries a jail term of up to 20 years.
Anwar Ibrahim declares new dawn for Malaysia after release: - Anwar Ibrahim declared a "new dawn for Malaysia" who come as he released from the jail on the last Tuesday following receiving a royal pardon, road surface the way for his return to the national politics.
"The pardons board has already met and the king has granted a full pardon, which means all past convictions have been expunged", said Sivarasa Rasiah, Anwar's lawyer. "Why should I harbour any malice towards him?"
"The King decreed that it was rare to find a politician that honour a promise despite being given the opportunity", Anwar said in his speech at a gathering to celebrate his release from jail at Padang Timur.
Mahathir said the government was also committed to repaying any debts linked to the fund that it has guaranteed.
World Health Organization urges ban on industrial trans-fats by 2023
It also wants trans fats content in the food supply and changes in trans fat consumption in the population Assessed and monitored. The country has witnessed improvement in the citizens' health and a reduction in deaths by way of cardiovascular disease.
Mahathir also seemed to be racing ahead with investigations into the 1MDB affair.