(Adds Bainimarama address, judge quotes)
SUVA, April 11 (Reuters) - Fiji's president reappointed former coup leader Commodore Frank Bainimarama to head the politically unstable South Pacific nation's government on Saturday, less than two days after a court ruled his 2006 coup illegal.
Fiji has suffered four coups and a bloody military mutiny since 1987, mainly as a result of tensions between the majority indigenous Fijian population and the economically powerful ethnic Indian minority.
Bainimarama was sworn in as caretaker prime minister in the morning by President Ratu Josefa Iloilo, who on Friday annulled the 1997 constitution and sacked the entire judiciary, including the judges who declared Bainimarama's former government illegal on Thursday.
"He just came, he read the oath and he was appointed as prime minister," a local journalist told Reuters by telephone.
In the afternoon Bainimarama, who is also military chief, reappointed nine ministers in his former government to the same posts. They were sworn in by the 88-year-old Iloilo, an ethnic Fijian like Bainimarama.
Bainimarama came to power in a bloodless coup in 2006. On Thursday, in a case brought by former prime minister Laisenia Qarase, the Court of Appeal overturned an earlier judgement that the military chief's government was legal, and called for a new government led by neither man pending fresh elections.
Bainimarama initially said he would step down.
But after annulling the constitution on Friday, the president enacted emergency powers for the country's military and police, initially for 30 days but with the possibility of extension.
Iloilo also issued a decree giving himself the power to appoint a prime minister by decree and other ministers on the advice of the prime minister. These powers are to remain in force until a parliament is elected under a new constitution yet to be adopted.
Iloilo has called for fresh elections in 2014. However, his actions have been widely criticised overseas.
UN secretary general Ban Ki-moon has criticised the annulment of Fiji's constitution and called for it to be reversed.
Despite the political upheavals, the situation in Suva has remained generally calm for the Easter weekend.
In an address to the nation on Saturday, Bainimarama called for all sections of society, including the media, to cooperate with the emergency regulations and promised elections by September 2014.
He said Iloilo had no choice but to abrogate the constitution as a result of the "anomaly" in the judges' decision and "the serious consequent vacuum created by that decision".
One of the three judges involved in Thursday's decision, Australian Randall Powell, warned of a legal vacuum in Fiji as a result of the president's suspension of the judiciary, with large numbers of cases potentially going untried. Powell has returned to Australia since the decision.
"It seems that Commodore Bainimarama has shown his true colours," Powell told Australia's SBS television.
IMPACT ON ECONOMY
Australian Trade Minister Simon Crean said on Saturday the events in Suva were likely to further damage Fiji's economy, which has suffered since the coup. On Thursday, the Reserve Bank of Fiji predicted that the economy would contract by 0.3 percent in 2009, compared with an expansion of 2.4 percent in 2008.
A leading analyst said Fiji could expect tightening of sanctions and action from both the Commonwealth and the Pacific Islands Forum, while tourists were likely to be scared off.
"It is certainly a circumvention of any democratic process, or any return to democratic process. It also shows that Fiji is not a country at the moment that is governed by the rule of law," analyst Damien Kingsbury told Reuters.
"Fiji also relies heavily on tourism. I think tourists these days are increasingly gun shy," added Kingsbury, associate professor in the School of International and Political Studies at Australia's Deakin University.
A former British colony, Fiji has been wracked by ethnic divisions ever since independence in 1970. A 1990 constitution cemented ethnic Fijian rule of Fiji and led to heavy emigration by ethnic Indians.
The 1997 constitution annulled on Friday was seen as more equitable, but quickly led to the election in 1999 of a government led by an ethnic Indian.
A civilian-led coup in 2000 was followed by elections in 2001 and 2006, but civilian rule ended in December 2006 when Bainimarama's coup overturned Qarase's government. (Editing by David Fox)