Sri Lanka's Prime Minister Ranil Wickremesinghe leaves after his swearing-in ceremony in Colombo, on August 21, 2015
UN chief Ban Ki-moon has urged Sri Lanka's new government to ensure "long term peace" as Prime Minister Ranil Wickremesinghe was set to form a coalition committed to ethnic reconciliation.
"The secretary-general encouraged the prime minister and the national unity government to seize this opportunity to advance long-term peace for all Sri Lankans," the UN said in a statement.
It added Ban had a telephone conversation with Wickremesinghe after he was sworn in at a ceremony in Colombo on Friday.
The UN statement received Saturday said Ban congratulated Wickremesinghe and commended his message of "good governance and national unity".
"He (Ban) noted that the peaceful nature of the polls as well as high voter turn-out were in part a reflection of this message," the UN said.
The UN welcome came as France said Sri Lanka's election was "one more step forward towards strengthening democracy".
"We hope it will also help continue the action taken since the election of President Maithripala Sirisena (in January) in support of human rights and inter-community reconciliation," the French foreign ministry said.
The opposition Sri Lanka Freedom Party (SLFP) of former president Mahinda Rajapakse agreed Friday to a broad-based coalition government with Wickremesinghe's United National Party (UNP).
The UNP, which more than doubled its seats in Monday's parliamentary election, is due to form a new cabinet early next week that will include SLFP members too after securing a coalition agreement.
The deal is a remarkable turnaround for a country that appeared firmly in Rajapakse's grip until his surprise defeat in January's presidential polls.
The former strongman, who oversaw the crushing of a long-running Tamil separatist insurgency, will sit on the opposition benches along with a dissident group of loyalists.
But the SLFP, which had opposed any concessions to the Tamils, now says it will back constitutional reforms aimed at addressing minority rights and ensuring reconciliation.
In a memorandum of understanding, the two parties pledged to ensure "ethnic and religious reconciliation" in a country that still bears the scars of a separatist war that killed at least 100,000 people between 1972 and 2009.
The agreement pledges constitutional reforms to ensure ethnic unity and uphold the rights of minorities.
But it does not go into specifics and it remains unclear how the two parties will reconcile past differences, with the UNP favouring extensive devolution of power to the Tamils.
The SLFP also opposes investigations into war crimes said to have been committed by troops under Rajapakse's command, while the UNP wants a fresh inquiry.
The minority Tamil National Alliance (TNA), which took 16 seats and emerged as the third largest party in a hung parliament, will not join the coalition but has promised the new government "issue-based" support.