President Maithripala Sirisena administered the oath that returned Wickremesinghe to office, then gave a speech soon after the ceremony, telling the prime minister and a group of his lawmakers that he can't find people of honesty and integrity to help him take the country forward.
"With the issues we have, I am not sure what guarantees we have that we could go on this journey together," Sirisena told Wickremesinghe.
The swearing in took place privately, with only a few lawmakers in attendance and media not permitted. It initially indicated an end to the impasse, but Sirisena's speech is a sign of more acrimony, possibly leading to early parliamentary elections. A new Cabinet is expected to be sworn in soon.
Wickremesinghe spoke separately at his official residence and refrained from responding to Sirisena. "Now I will assume duties of the office of prime minister," Wickremesinghe told his cheering supporters.
"Unfortunately, during the past few weeks, the progress of this country and the development programs that we undertook were stalled," he said. "Not only that, the country went backward. Today we commit firstly to bring back normalcy and resuming the development program."
In his televised speech, Sirisena said his reasons for firing Wickremesinghe included a lack of interest in helping investigate an alleged insider trade during a bond issue, in which a former Central Bank governor who is a close friend of Wickremesinghe is implicated.
He also said Wickremesinghe's ministers alienated Buddhist monks by having them arrested for keeping unlicensed captive elephants at temples. Sri Lanka is a predominantly Buddhist nation with an influential clergy.
Sirisena also criticized Wickremesinghe for investigations into alleged abuses during the long civil war that ended in 2009. The president said Wickremesinghe had only government soldiers arrested but had not looked into prosecuting former Tamil Tiger rebels he said were hiding in foreign countries.
"My view is that we should prosecute everyone, or else we should negotiate with the international community and free our soldiers (from accusations)," he said.
Both sides were accused of grave wartime abuses. According to a U.N. report, at least 40,000 ethnic Tamil civilians were killed just in the final months of the fighting.
Wickremesinghe had insisted his abrupt firing on Oct. 26 was unlawful. Sirisena's choice for prime minister, former strongman Mahinda Rajapaksa, lost two no-confidence votes in Parliament but continued to hold the office with Sirisena's support.
When his opponents went to court, the Court of Appeal suspended Rajapaksa and his Cabinet from functioning in their offices. Rajapaksa asked the Supreme Court to lift the suspension, but it refused and extended the suspension until mid-January, forcing Rajapaksa to resign on Saturday.
The suspension had left Sri Lanka without a government and in danger of being unable to spend government money from Jan. 1. It is also committed to repay $1 billion in foreign debts in January.
"We can be proud of the way our Parliament and Supreme Court did their duties according to the law," Wickremesinghe said Sunday, adding that the Supreme Court had strengthened the freedom of the citizens by interpreting the law accurately.
"We all need a normal life, we need our progress and it is to this that we are committed," he said.
Sirisena was health minister in Rajapaksa's Cabinet when he defected to join Wickremesinghe and challenge Rajapaksa in the 2015 presidential election. After winning the election, he formed a government with Wickremesinghe as prime minister, but the two leaders started to have differences over economic policy and the investigations of alleged wartime abuses.