Mahinda Rajapaksa staged a dramatic political comeback on Friday, becoming Sri Lanka's new Prime Minister after President Maithripala Sirisena sacked premier Ranil Wickremesinghe, triggering angry reactions from the finance minister who termed the former strongman's return as an "anti-democratic coup".
Visuals of the former president Rajapaksa taking oath as the premier were released to media and was shown on TV channels.
Rajapaksa, 72, tweeted a photo of him and Sirisena after the swearing in ceremony.
"Former #SriLanka President Mahinda Rajapaksa sworn in as new Prime Minister," he said in the tweet.
The sudden development came after Sirisena's broader political front United People's Freedom Alliance (UPFA) announced that it has decided to quit the current unity government with prime minister Wickremesinghe's United National Party (UNP).
Mahinda Amaraweera, agriculture minister and the general secretary of the UPFA, told reporters that the UPFA decision has been conveyed to Parliament.
Reacting sharply to the development, Minister of Finance and Media Mangala Samaraweera said that the appointment of Rajapaksa as the prime minister is "unconstitutional and illegal".
"This is an anti democratic coup," he said in a tweet.
The unity government was formed in 2015 when Sirisena was elected President with Wickremesinghe's support, ending a nearly decade-long rule by Rajapaksa.
The sudden political development ends an over three-year-old coalition government that was formed by Sirisena and Wickremesinghe on a promise to combat corruption and financial irregularities.
Sirisena, who was Rajapaksa's minister of health, broke away from him to contest the presidential elections.
Political analysts said Sirisena's move to install Rajapaksa as the prime minister could lead to a constitutional crisis as the 19th amendment to the Constitution would not allow the sacking of Wickremesinghe as the premier without a majority.
Rajapaksa and Sirisena combine has only 95 seats and is short of a simple majority. Wickremesinghe's UNP has 106 seats on its own with just seven short of the majority.
There was no immediate comment from Wickremesinghe or the UNP.
President Sirisena's party withdrew from the ruling coalition after simmering tensions between him and Wickremesinghe.
The unity government was thrown into a crisis after Rajapaksa's new party pulled off a stunning victory in local elections in February seen as a referendum on the ruling alliance.
Last week, it was reported that Sirisena accused his senior coalition partner the UNP of not taking seriously an alleged conspiracy to assassinate him and Gotabhaya Rajapaksa, the former top defence ministry bureaucrat and brother of ex-president Mahinda Rajapaksa.