The former PM Mahathir Mohamad, considered a political survivor, is on course to become the world's oldest elected leader at 92, after victory in Malaysia's bitterly fought election.
He will become Malaysia's prime minister again. Mr Najib has said he will "accept the verdict of the people". "Yes, yes, I am still alive," Mr Mahathir told a news conference in the early hours of Thursday. No single party within the coalition won a majority, so it now rests with Malaysia's king to decide who forms a government.
Image from Malaysia
The official results showed the opposition Pakatan Harapan - the Alliance of Hope - secured 113 of the 222 seats being contested, including some which have only ever been held by the government. BN took 79 seats. Mr Mahathir joined UMNO at the age of 21 and ran a medical practice for seven years in his home state of Kedah before becoming a member of parliament in 1964. He was prime minister, at the head of the BN coalition, for 22 years, from 1981 until he stepped down in 2003. Under his rule, Malaysia transformed into one of the Asian economic tigers of the 1990s. His authoritarian but pragmatic policies won him popular support. To the surprise of many, he has admitted he was wrong on many things. Mr Mahathir was also a mentor to Mr Najib, who became prime minister in 2008.