Wickremesinghe returns as Sri Lanka's prime minister

* Wickremesinghe sworn in as PM before Sirisena

* Sirisena had vowed not to appoint Wickremesinghe as PM

* Rajapaksa resigned as PM on Saturday as a govt shutdown loomed

* Rajapaksa had failed to secure parliamentary majority (Recasts with Wickremesinghe's swearing-in)

Ranil Wickremesinghe was sworn in as Sri Lanka's prime minister on Sunday, making a remarkable comeback weeks after being ousted by President Maithripala Sirisena under controversial circumstances.

Wickremesinghe's reinstatement, which is expected to end a political crisis that began in late October when he was surprisingly sacked, is an embarrassment for the president.

Sirisena had replaced Wickremesinghe with former president Mahinda Rajapaksa following differences over policy matters and other issues. However, Rajapaksa failed to win a parliamentary majority and resigned on Saturday as a government shutdown loomed.

Sirisena had repeatedly said he would not reappoint Wickremesinghe as prime minister. But he had to change his stance to gain parliamentary approval for a temporary budget that is required by Jan. 1.

The swearing-in ceremony was closed to the media and only a few lawmakers from Wickremesinghe's coalition were present, an official in the president's office told Reuters. The official did not want to be named.

Wickremesinghe, who has never completed a full term as prime minister, was appointed for the post for the fifth time.

The government's Information Department confirmed that Wickremesinghe had been sworn in by Sirisena. Lawmakers from Wickremesinghe's party earlier told Reuters he would take charge as prime minister starting Sunday.

The South Asian island country's parliament voted to cut the budget for Rajapaksa and his ministers after Sirisena refused to accept no-confidence votes against Rajapaksa, saying that due process was not followed.

The Parliament already passed a confidence vote in Wickremesinghe while it sought his reinstatement as prime minister to defuse a constitutional crisis.

On Friday, Sri Lanka's Supreme Court rejected Rajapaksa's bid for an injunction against a lower court's order that barred him and his Cabinet from performing their roles.

Many foreign countries refused to recognise Rajapaksa's government. Credit rating agencies Fitch and Standard & Poor's downgraded Sri Lanka, citing refinancing risks and an uncertain policy outlook.

Sirisena came to power in 2015 on a pledge to uphold democracy and stamp out corruption. However, his popularity has been hit by a crisis many say he triggered because of personal differences with Wickremesinghe.

Much of the conflict between the two men centred on a dispute over how much to accommodate Indian interests in the country versus Chinese, government officials and foreign diplomats told Reuters last month.

China has been investing heavily in the country though India is the traditional power in the region.