UPDATE 1-Malaysia's ousted PM says to take a break amid reports of flight

(Adds further details from Najib's tweets, background)

KUALA LUMPUR, May 12 (Reuters) - Former Malaysian Prime Minister Najib Razak said on Twitter that he would take a short break to spend time with his family, hours after it emerged that his name was on the flight manifest of a private jet scheduled to leave for Jakarta on Saturday morning.

"After over four decades in politics and the recent election campaign, which was regrettably personal and perhaps the most intense in Malaysian history, I will take a short break to spend time with my family whom I have not seen enough of in recent years," Najib said in a tweet.

Najib, 64, lost to former Prime Minister Mahathir Mohamad in this week's general election.

Mahathir has vowed to investigate a multi-billion-dollar graft scandal at state fund 1Malaysia Development Berhad (1MDB), which was founded by Najib. Najib has consistently denied any wrongdoing in connection with 1MDB.

The Wall Street Journal, citing people close to Mahathir, reported earlier on Saturday that Najib would be prevented from leaving the country. Reuters was unable to verify the report.

The manifest of the jet, which is scheduled to fly from an airport near Kuala Lumpur to the Indonesian capital at 10:00 a.m. (0200 GMT), names Najib and his wife, Rosmah Mansor, as the only two passengers, two sources and two media reports said earlier.

A source in Mahathir's government told Reuters that Najib would be taking a holiday. Malaysiakini, a news portal, cited an unnamed source close to Najib as saying that he would take a two-day break in Indonesia.

"I APOLOGISE FOR ANY SHORTCOMINGS"

Mahathir, previously prime minister for 22 years, was once Najib's mentor but turned against him over the 1MDB scandal and led the opposition challenge to him in this week's election, defeating the coalition that had ruled Malaysia for six decades.

In another tweet, Najib said he was praying that, "after this divisive period", Malaysia would unite.

"I apologise for any shortcomings and mistakes, and I thank you, the people, for the opportunity to lead our great nation."

Najib may be remembered most for the scandal over 1MDB, whose advisory board he chaired until 2016.

News broke in 2015 that about $700 million allegedly stolen from 1MDB had made its way into his personal bank accounts.

He denied any wrongdoing and was cleared by Malaysia's attorney-general, even as U.S. authorities alleged that over $4.5 billion was stolen from the fund in a fraud orchestrated by a financier known to be close to Najib and his family.

U.S. Attorney-General Jeff Sessions called the 1MDB scandal "kleptocracy at its worst" and the fund is the subject of money-laundering investigations in at least six countries, including Switzerland, Singapore and the United States.

Filings by the U.S. Justice Department in a civil lawsuit indicated nearly $30 million of the money stolen was used to buy jewellery for the prime minister's wife, Rosmah, including a rare 22-carat pink diamond set in a necklace.

Two sources told Reuters on Friday that Mahathir will appoint a finance ministry adviser to oversee the recovery of billions of dollars allegedly stolen from 1MDB.

Mahathir said after his victory in Wednesday's election that he would not be looking for a scapegoat in the scandal.

"We are not seeking revenge," the 92-year-old prime minister said. "What we want is to restore the rule of law ... if the law says that Najib has done something wrong, then he will have to face the consequences."

Mahathir is expected to announce his cabinet line-up later on Saturday. (Writing by John Chalmers Additional reporting by Emily Chow, Liz Lee and Joseph Sipalan; Editing by Diane Craft)