KUALA LUMPUR - Malaysia's former prime minister Najib Razak has been barred from leaving the country after he announced plans to take a short holiday following the shock defeat in this week's general election.

"I have been informed that the Immigration Department has barred me and my family from going overseas. I respect the decision and will be with my family in the country," Mr Najib said in a Facebook post late Saturday (May 12) morning.

Mr Najib, 64, had earlier said he was taking a short break "to spend time with my family whom I have not seen enough of in recent years".

In a Facebook post late Saturday morning, Malaysia's immigration department confirmed that Mr Najib and his wife Rosmah Mansor have just only been blacklisted from leaving the country.

Mr Najib and his wife were listed as passengers on the flight manifest of a private jet scheduled to leave Kuala Lumpur for Jakarta at 10am on Saturday, local media reported earlier.

Dozens of journalists had gathered at Subang Airport on Saturday morning after viral posts circulated on social media about Mr Najib and Ms Rosmah leaving Malaysia. Police were seen guarding the airport when The Straits Times arrived.

According to Malay Mail, the private flight has been cancelled pending further instructions, following the appearance of a mob at the airport.

"It's due to security reasons and the crowd here this morning. We still need to ensure the security of everyone. Emotions are running high and we can't allow the public to take matters into their own hands," the source told Malay Mail.

The jet was scheduled to fly to Halim Perdanakusuma International Airport in the Indonesian capital at 10am local time, the sources and news reports said.

However, when The Straits Times checked with an officer at Halim Perdanakusuma International Airport in east Jakarta on Saturday morning, he said there was no such incoming flight as reported in the media.

In an earlier Facebook post on Saturday morning, Mr Najib thanked Malaysians for the opportunity to lead the country and apologise for "any shortcomings and mistakes".

"My Barisan Nasional colleagues and I are committed to respecting the will of the people and facilitating a smooth transfer of power. The best interests of Malaysia and its people will always be my first priority and I intend to continue serving them in whatever capacity I can.

"I pray that after this divisive period, the country will unite. I apologise for any shortcomings and mistakes, and I thank you, the people, for the opportunity to lead our great nation.

"It has been the honour of my lifetime to serve you and Malaysia," he wrote.

Malaysiakini had earlier reported that Mr Najib and Ms Rosmah were blacklisted by the Immigration Department, based on a search on the department's Travel Status Enquiry System (SSPI). The database allows Malaysians to check if they are cleared to travel to East Malaysia or overseas.

But Immigration Department director-general Mustafar Ali denied that the duo had been blacklisted.

"Not blacklisted for now," he told Malaysiakini in a text message. He refused to elaborate.

On Friday, a day after he was sworn in, Prime Minister Tun Dr Mahathir, 92, vowed to investigate a multi-billion-dollar graft scandal at state fund 1Malaysia Development Berhad (1MDB), which was founded by Mr Najib.

Mr Najib has consistently denied any wrongdoing in connection with 1MDB.

The Umno-led Barisan Nasional coalition suffered a shocking defeat on Wednesday night in the country's 14th general election, winning only 79 seats in Parliament from 133 in 2013.

Several Umno leaders have called for reform, hinting towards appointing a new party president during its internal elections, which would likely be held by year end.

The party is constitutionally slated to hold its polls every three years, but this has been delayed by two years.

"To return to the original Umno, we must undergo a major change within," Umno Youth chief Khairy Jamaluddin said in a statement.

He added that changes needed include "absolute honesty, outstanding courage and painful sacrifice".

Calling for the "rebuilding of the party" and for Umno to return to its "original spirit", Mr Khairy finds his words echoed by Umno Youth leaders nationwide.

Umno Youth from seven states have called on Mr Najib to step down from a post he has held since 2008, when he won uncontested at party elections.