ACF says it is not satisfied with the murder probe

Spokesman for Action Against Hunger (ACF) , Andrew Mitchell, told BBC Sinhala that one month on, the inquiry was still only at a preliminary stage.

"Like many people in the international community, we are waiting for an official response from the government.

We are waiting for a proper investigation to uncover the facts, and today, one month later, they're still at a preliminary stage -- they still haven't opened, officially, the investigation."

We are waiting for a proper investigation to uncover the facts, and today, one month later, they're still at a preliminary stage -- they still haven't opened, officially, the investigation Action Against Hunger

A legal representative for families of the murdered aid workers, K Rathnavel, on Tuesday expressed concern that the investigation has been transferred to Anuradhapura magistrate’s court from Trincomalee.

International truce monitors in Sri Lanka have concluded that government troops killed the aid workers, all of them Sri Lankan.

SLMM findings

The Sri Lanka monitoring Mission (SLMM) said the fact that the security forces prevented access to monitors to the scene of the murder meant that the forces were implicated in the murder.

The deaths this month of the Action Against Hunger workers were "a gross violation of the ceasefire accord by the security forces", monitors said.

They have no right to make such a statement because they are not professionals in autopsy or post-mortem Minister Keheliya Rambukwella

They were "convinced" no other armed group could have been behind the killings near Muttur in the north-east.

A government spokesman angrily rejected the allegation, calling it "pathetic and biased".

The Sri Lankan government has categorically denied any responsibility.

Minister Keheliya Rambukwella told AP news agency: "We deny it and it's a totally baseless statement that the head of the SLMM has made.

"They have no right to make such a statement because they are not professionals in autopsy or post-mortem."

The aid staff - all but one ethnic Tamils - were working on tsunami relief projects in an area that had seen several days of fighting between Tamil Tiger rebels and government troops.

A statement released by Maj Gen Ulf Henricsson, the head of the SLMM, said he had held "confidential conversations with highly reliable sources" on who was most likely to have been responsible for the killings.

"The views have not proved contradictory and the security forces of Sri Lanka are widely and consistently deemed to be responsible for the incident," he said.