Papua New Guinea Prime Minister Peter O'Neill has been served with an arrest warrant in relation to a fraud case, the head of the South Pacific country's anti-corruption body says.

The warrant relates to allegations that O'Neill personally authorised the illegal payment of about $30m in government money to law firm Paul Paraka Lawyers, Investigation Task Force Sweep chairman Sam Koim said on Monday.

O'Neill has previously denied the allegations, arguing that a letter produced by the PNG opposition as evidence that he had authorised the payment was forged.

A senior officer at Port Moresby Police Headquarters said a letter signed by Police Commissioner Tom Kulunga requesting a formal record of interview was delivered to O'Neill on Monday.

The officer, who declined to be named because of the political sensitivity of the case, said O'Neill was offered two potential appointment times on Monday, but failed to show up to either.

O'Neill was then asked to suggest a suitable time for the police interview, but had yet to reply, the officer said.

"If he doesn't come in, we'll be forced to bring him in," the officer said. The officer did not specify a deadline.

O'Neill told Australia's SBS News that the warrant against him was politically motivated. "There is a lot of political movement in the country," he said.

"We have strong confidence in the judiciary up here; there is a very vibrant judiciary that will hear the matter and the truth will come out," he said.

The Investigation Task Force Sweep, which O'Neill created in 2011 as part of his anti-corruption drive, charged Paul Paraka Lawyers in October last year with offences including conspiracy to defraud, stealing by false pretense and money laundering.

The firm allegedly submitted fraudulent bills for legal work performed for the government.

Source: AP