Image copyright AFP Image caption Mr Najib has denied all wrongdoing after reports that almost $700m (£450m) were transfered into his personal account

The scandal surrounding Malaysia's state development fund 1MDB has gripped the country for years.

Now the US has said it is moving to seize more than $1bn (£761m) in assets, ranging from plush properties to a private jet, from people connected to the country's Prime Minister Najib Razak.

The asset seizure by the US would be the largest ever by the Justice Department's anti-corruption unit.

This is how the story has played out so far.

What is the controversy about?

Image copyright Reuters

1Malaysia Development Bhd, set up by Mr Najib in 2009, was meant to turn Kuala Lumpur into a financial hub and boost the economy through strategic investments.

But it started to attract negative attention in early 2015 after it missed payments for some of the $11bn it owed to banks and bondholders.

Then the Wall Street Journal (WSJ) reported it had seen a paper trail that allegedly traced close to $700m from the fund to Mr Najib's personal bank accounts.

Why is the US intervening now?

The Department of Justice alleges $3.5bn (£2.6bn) was misappropriated from 1MDB.

"The Malaysian people were defrauded on an enormous scale," Deputy FBI Director Andrew McCabe said at a news conference.

Mr Najib is not named in the suit. But it refers to "Malaysian Official 1", described as "a high-ranking official in the Malaysian government who also held a position of authority with 1MDB".​

The move reflects an intention by the US to open new fronts in its fight against illicit finance.

It also sets up a rare confrontations between the US and Malaysia, which is considered an important partner in the fight against terrorism.

What do people involved say?

1MDB responded to the US papers by saying it had not benefited from the various transactions described in the suit.

The fund has repeatedly asserted that it has never given money to the prime minister and called the claims "unsubstantiated".

Mr Najib has also consistently denied taking money from 1MDB or any public funds.

His office said Malaysia had "led the way in investigations into 1MDB" and would "fully co-operate with any lawful investigation".

Is anyone else involved?

Mr Najib has accused his fiercest critic, former Prime Minister Mahathir Mohamad, of using the scandal as a means of "political sabotage".

He claims Mr Mahathir worked "hand in glove" with foreigners as part of a campaign "to topple a democratically elected prime minister."

The BBC put Mr Najib's allegations to Mr Mahathir, who dismissed the claims. Instead, he called on the prime minister to show proof that he didn't pocket state funds.

Over the last year, Mr Najib has also sacked his deputy Muhyiddin Yassin and replaced the former attorney-general over critical comments they made about the scandal.

Image copyright AP Image caption Authorities seized computers when they raided 1MDB offices

There have been multiple domestic official investigations into the 1MDB fund, including a special task force headed by the attorney general. The team raided the office of 1MDB in 2015 and took away some documents.

But the replacement attorney general cleared Mr Najib of wrongdoing in January.

Multiple foreign authorities have also been investigating the company.

In May, Singapore ordered Swiss bank BSI to shut down in the city-state for breaking its money-laundering laws in its dealings with 1MDB.

Swiss authorities have opened criminal proceedings related to 1MDB on "suspected corruption of public foreign officials, dishonest management of public interests and money laundering".

What do Malaysians think about it?

Former Prime Minister Mahathir Mohamad said Malaysians should push for a referendum on the prime minister's leadership.

Opposition leader in parliament, Wan Azizah Wan Ismail, called upon Mr Najib to give a full explanation in parliament and go on leave so a full probe could take place.

Civil society group Bersih said Mr Najib and the attorney-general who in January had cleared the prime minister should both resign immediately to make way for independent investigations.

The 1MDB controversy has frustrated many Malaysians who are struggling with the rising cost of living and what is perceived to be ingrained corruption in its political system.

Last year tens of thousands of protesters took to the streets calling for the resignation of the PM.

However, thousands have also rallied in support of the government.

The reaction on Thursday to the US move was muted in both Malaysia's mainstream newspapers and social media.

Malaysia's government has cracked down on reporting of the 1MDB scandal, blocking access to certain online news portals and targeting media groups and journalists.