Malaysia's crisis-hit state investment fund 1MDB said Tuesday it has been given more time to pay more than $600 million to Abu Dhabi to settle debts after missing a second deadline.

1MDB and its founder, Prime Minister Najib Razak, are battling allegations that billions were looted from the fund in complex overseas deals that are being investigated by authorities in several countries.

Both the fund and Najib have vehemently denied wrongdoing.

1MDB agreed in April to pay Abu Dhabi's sovereign wealth fund, International Petroleum Investment Company (IPIC), about $1.2 billion to settle debts.

Half was due to be paid at the end of July and the rest by the end of the year, IPIC said at the time. 

1MDB missed the first deadline last week and was given five more days to make the payment before becoming subject to additional obligations.

But Irwan Serigar Abdullah, chairman of 1MDB's board of directors and Malaysia's treasury secretary-general, said IPIC had agreed to give the fund more time to pay.

"We are asking for an extension which they have agreed and when the time comes, we will pay," he was quoted as saying by national news agency Bernama. 

He did not say how much extra time 1MDB had been given.

When it missed the first deadline, 1MBD said it was awaiting fresh funds and pledged to make the payment in August.

1MDB and the Abu Dhabi fund had been involved in a dispute that extended to repayments on two sets of bonds issued by the Malaysian fund.

In April 2016 1MDB defaulted on $1.75 billion in bonds after missing an interest payment of $50 million.

In June that year Abu Dhabi announced it was seeking $6.5 billion from the Malaysian fund through international arbitration.