(AFP) - A UK court on Thursday ordered the Nigerian government to pay $200 million pending its appeal against the $9.6 billion awarded to a tiny firm over a failed natural gas deal.

The high-stakes dispute pits Process and Industrial Developments Limited (P&ID) -- a British Virgin Islands-registered firm founded by two Irish business partners -- against an energy-rich but politically-troubled nation of 200 million people.

The original settlement against the Nigerian government represents around a fifth of the foreign reserves held by Africa's largest economy.

Justice Christopher Butcher of the Commercial Court in London granted the Nigerian government a stay of execution of the fine pending an appeal.

But he also gave the government 60 days to make a $200-million security payment -- and 14 days to pay running costs whose sum was not disclosed in court.

Justice Butcher said P&ID had the right to seize Nigerian assets should either of those deadlines be missed.

The justice based his decision on the "real risk" that Nigeria's "assets will not be returned in the event that the appeal is successful and would be lost to the government and to the people of Nigeria".

He added that there was the "risk of immediate, serious and potentially irreparable damage" should P&ID use "third-party agents" to monetise and stash away the assets seized pending an appeal.

Justice Butcher further ruled "that there may be immediate and potentially severe damage to Nigeria if there is no stay".

The appeal relates to a running dispute over which country's court -- and law -- has jurisdiction over the explosive case.

Government lawyer Harry Matovu claimed Nigeria's "sovereign immunity rights" were being violated by the settlement amount.

The original contract in 2012 required the Nigerian government to pay $300 million for P&ID to set up a way to turn a dirty form of natural gas burned off during oil production into electricity for local government use.

The deal fell through amid mutual recriminations and claims of fraud. The $9.6 billion represents money that added up through accrued interest payments.

© Agence France-Presse