UK rights group, Freedom From Torture called on newly elected Sri Lankan President Maithripala Sirisena to cooperate with the UN investigation into mass atrocities on the island and ensure justice is served for human rights violations.

"Sri Lanka's new president, Mr Sirisena, needs to face up to the human rights violations that have been perpetrated during and since the end of the civil war, rather than hoping they will go away. Hundreds of thousands of people were affected by this brutal civil war and healing can only truly begin when justice is done," Susan Munroe, Chief Executive of Freedom from Torture, said in a blog post entitled “Election fever will fade, but the need for justice will not."

The British Foreign Secretary, Philip Hammond, congratulated newly elected president Maithripala Sirisena and said "Sri Lanka has a renewed opportunity now to grow as a stable, prosperous and inclusive country, reflecting the wishes of all its people."

"I commend the people of Sri Lanka on the successful completion of their elections and offer my congratulations to Maithripala Sirisena. Sri Lanka has a renewed opportunity now to grow as a stable, prosperous and inclusive country, reflecting the wishes of all its people," the Foreign Secretary said in a statement released on Friday.

British Prime Minister David Cameron, congratulating Maithripala Sirisena, called on the the new president to "support the ongoing UN Office of the High Commission for Human Rights investigation into human rights abuses."

In a statement released by Downing Street on Friday, Cameron said:

"I congratulate Maithripala Sirisena on his victory in yesterday’s Presidential election.

The British opposition party's shadow foreign office minister, Kerry McCarthy, urged Sri Lanka’s new government to cooperate with the Untied Nations inquiry into mass atrocities and urged the UK “to do everything it can to support the UN investigation.”

Condemning the previous regime's treatment of ethnic communities on the island she said, "minority groups were repressed, freedom of expression denied, torture and enforced disappearances common amongst the Tamil community, and human rights defenders threatened."

Canada's Liberal Party has called on the newly elected president Maithripala Sirisena to "work with the international community to achieve accountability", as well as to demilitarise the Northeast and introduce comprehensive devolution.

In a statement congratulating Sirisena, Marc Garneau, Foreign Affairs Critic for the Liberal Party, expressed hope that "that the President Elect will work to ensure that democracy and the rule of law is restored, freedom of religion is respected, and the north and the east are demilitarized."

The new president Maithripala Sirisena must stop the “vicious military occupation of the north,” and perpetuation of “genocide against the Tamil population,” whilst allowing Tamils to “determine their own future,” said the Tamil Refugee Council (TRC) in Australia.