A French charity urged the Sri Lanka’s government to hold a credible investigation into the killing a decade ago of 17 of its staff. The head of Action Against Hunger (ACF) said it was time for Sri Lanka to act on its promises as she visited the island to mark the 10th anniversary of the massacre.

No one has ever been prosecuted over the execution style killings of ACF staff, among them four women, the worst attack against humanitarian workers during the island’s 37-year-long ethnic war.

Human Rights Watch has said mishandling of the case by successive Sri Lankan governments showed the need for credible international involvement to determine who carried out the killings. ACF Chief Executive Veronique Andrieux said the charity was closely monitoring Colombo’s pledge at the UN Human Rights Council in September to establish an internationally acceptable mechanism to prosecute war criminals.

“What we hope is that this accountability mechanism will be able to deliver a credible legal and just solution,” Andrieux told media. “We are awaiting concrete steps in the right direction. It is now time for action.”

The workers, all Sri Lankan, were massacred near Trincomalee, at a time when government forces were locked in combat with separatist Tamil Tiger rebels in the area. Andrieux said the ACF had held a private remembrance event in the capital on Wednesday.