The "Malaysian Official 1 [MO1]" who was named more than 30 times in a US Department of Justice (DoJ) lawsuit in July is embattled leader Najib Razak, a senior government official has revealed.

The legal action filed by the DoJ seeks to seize assets it says were acquired with more than $3.5bn (£2.6bn, €3.1bn) allegedly funnelled away from the 1Malaysia Development Berhad (1MDB) state fund. "The Department of Justice will not allow the American financial system to be used as a conduit for corruption," US Attorney General Loretta declared as she announced the civil suit.

"Corrupt officials around the world should make no mistake that we will be relentless in our efforts to deny them the proceeds of their crimes," she added.

In a BBC interview broadcast on Thursday (1 September), Abdul Rahman Dahlan, a senior minister in Razak's cabinet, confirmed suspicions that have been long-held by many Malaysians. "I agree that 'MO1' is the prime minister," he said. "I've said it openly. Obviously if you read the documents, people say it is the prime minister.

"But when I have been asked this question, I always ask back: why didn't the DOJ name him by his proper name? That reason is because he is not part of this investigation," Dahlan added. "It is not about him. It is about a bunch of people who have been named... and the Department of Justice will take this to the courts and let the courts decide."

Dahlan said the difference between being referred to and named as a subject in a lawsuit is "black and white". He accused Razak's political rivals of "deliberately mixing the two up to deceive the Malaysian people".

Razak launched 1MDB in 2009 to boost Malaysia's economy through investments and infrastructure deals. Accusations of a global programme of embezzlement and money laundering involving billions of dollars siphoned from 1MDB started to attract attention two years ago, Agence France-Presse (AFP) noted.

Razak was investigated following claims that $681m was transferred was transferred into the Malaysian prime minister's bank account. In January 2016, the country's attorney general, Mohamed Apandi Ali, said the money was a "personal donation" from the Saudi royal family and not illegal. Ali added that $620m had been returned to the Saudi donor, the Wall Street Journal (WSJ) reported.

Razak has repeatedly denied any wrongdoing.

The Malaysian government did not respond to a request for comment.