The arrest of a Sri Lankan man by British war crimes police could set a precedent for the detention of current military officers or government officials, Colombo said Friday, calling it a "very big danger".
London's Metropolitan Police War Crimes team on Thursday announced the arrest of a 48-year-old man in Northamptonshire in connection with the 2000 murder of high-profile Tamil journalist Mylvaganam Nimalrajan on the Jaffna peninsula.
British police can investigate anyone who may fall under British jurisdiction and is suspected of committing war crimes, crimes against humanity, genocide or torture anywhere in the world under a "no safe haven" policy.
Sri Lanka has repeatedly been censured by the UN Human Rights Council, primarily in connection with events during the country's decades-long civil war.
Foreign ministry secretary Jayanath Colombage said the British move could threaten current office-holders.
"Invoking universal jurisdiction is another very debatable topic," he told reporters.
"Any country can use this as an excuse to target people of another country," he said, calling it a "very big danger".
"So we need to be prepared for that," he added.
No additional information about the man arrested in Britain has been released.
Western nations have imposed travel bans on Sri Lankan military officials, including current army chief Shavendra Silva, but Tuesday's arrest was the first carried out overseas over war crimes allegations in Sri Lanka.
Nimalrajan, 39, a local Tamil journalist who also worked for several media outlets, including the BBC, was shot dead at his home in the embattled Jaffna town in 2000. No one has been prosecuted for the murder.
Colombo has rejected a UN mechanism set up last year to preserve evidence following allegations that Sri Lankan troops killed at least 40,000 civilians in the final months of the war in 2009.