Sri Lanka has made "considerable progress" in the investigations into the assassination of foreign minister Lakshman Kadirgamar, a senior cabinet minister has said.

Cabinet spokesman and minister Nimal Siripala de Silva was Friday quoted by the Daily News as saying that there had been considerable progress in the investigations being conducted into Kadirgamar's slaying but details could not be divulged at this stage, Xinhua reported.

"This is because certain media attempt to psychologically kill people before the actual killing takes place," he said at the weekly cabinet briefing Thursday.

"That is why the government does not divulge such information. Before the assassination of Kadirgamar, certain media divulged the number of cars and even the description of the number plates of his cars and security vehicles, etc.

"Probably this would have helped the Liberation Tigers of Tamil Eelam (LTTE) to assassinate Kadirgamar. Taking into account what has happened in the past, we don't want to jump the gun and hamper the investigation," the minister said.

De Silva said Kadirgamar's slaying was a serious setback to the peace process. But the government was committed to go forward despite various brutal acts conducted by the LTTE.

Kadirgamar was shot dead as he was returning home after a swim on the night of Aug 12. No one has claimed responsibility for the assassination but the Tamil Tigers are the prime suspects though they have denied any involvement.