Sri Lankan President Maithripala Sirisena ousted the incumbent prime minister on Friday, replacing him with former president Mahinda Rajapaksa, a spokesman for the president's office said.
The move came hours after Sirisena's party, which formed part of a ruling coalition, decided to withdraw from the government.
The appointment of Rajapaksa effectively removes prime minister Ranil Wickremesinghe. The swearing-in ceremony was broadcast on television, while security was tightened around the president's office where the event took place.
The president constitutionally holds the powers to name the prime minister in Sri Lanka.
Sirisena was elected as president in 2015 largely thanks to support from Wickremesinghe's United National Party (UNP), but the coalition government has been plagued by infighting in recent months.
Sirisena defeated Rajapaksa in the 2015 election, ending his 10-year rule.
