Local and international rights groups urged Commonwealth leaders not to relax pressure on Sri Lankan President Mahinda Rajapakse to investigate war crimes after they leave a summit in Colombo Sunday.
Rajapakse spent much of the three-day summit deflecting calls for an international inquiry into the bloody finale to Sri Lanka's civil war in 2009, in which the UN says as many as 40,000 Tamil civilians may have been killed.
London-based Amnesty International said Sri Lanka may regret having hosted the event "which has proved a PR disaster" for Colombo.
It and other rights groups said it was vital that pressure on the Rajpakse regime should not melt away once the bloc's leaders fly home.
"The challenge for the international community is now to keep up the pressure on the Sri Lankan government," said Amnesty director Steve Crawshaw.
British Foreign Secretary William Hague met rights activists in Colombo on Sunday in a sign of London's determination to keep the issue in the spotlight.
Rajapakse has been infuriated by British Prime Minister David Cameron's warning that he will lead a push for an international probe through UN bodies unless an internal inquiry produces credible results by March.
"We cannot and will not turn a blind eye to the abuses which occur whether they are about freedom of expression, impunity for disappearances or sexual violence, freedom from torture and the lack of accountability," Hague said after his meetings in Colombo.
Rajapakse has also taken a hit from the decision by the leaders of India, Canada and Mauritius to boycott the summit. Canada's foreign minister even said the decision to allow Colombo to stage such as a gathering was akin to "accommodating evil".
But the leaders of other countries who did come to Colombo were much more wary of upsetting their hosts.
Australian Prime Minister Tony Abbott peppered calls for improvement in its rights record with an appeal to be "good mates" with Sri Lanka.
South African President Jacob Zuma refrained from criticising Colombo, but did offer "any assistance" in reconciliation efforts, based on his country's experience of addressing apartheid-era abuses through a truth and reconciliation commission.
Rajapakse has said Sri Lanka must be allowed to addresss its past on its own and in its own time.
But the Families of the Disappeared, a Colombo-based rights group, said Rajapakse could not be trusted to come up with results unless international pressure is applied.
The group's head Britio Fernando said pro-government activists broke up an exhibition they organised to coincide with the summit to highlight the thousands killed by security forces.
"The government is labelling anyone who speaks on behalf of human rights as a traitor," Fernando said.
"The international community must keep up the momentum and not accept Rajapakse at face value. He says one thing to the foreigners and does something else back home."
The local Centre for Human Rights said the summit had turned an unwelcome spotlight on the island's rights record and it hoped that the world would continue to pay attention.
"There will be a lot of pressure because this issue of rights in Sri Lanka has been re-broadcast to the world thanks to the summit," its chief Keerthi Tennakoon told AFP.
"If the government continues to ignore this pressure, there will be consequences."
Amnesty's Crawshaw said that those "responsible for past violations, including war crimes, must be held accountable irrespective of rank, and ongoing human rights violations stopped -- victims and survivors must see justice done".
Rajapakse has consistently maintained that no civilians were killed in the final stages of the war. He says he deserves credit for ending a conflict which claimed more than 100,000 lives.