European monitors of the ceasefire in Sri Lanka have ruled that Tamil Tiger rebels breached the accord by attacking a Sri Lankan navy vessel on Tuesday.
The Tiger boat "fired 75-100" rounds, Sri Lanka's military says
The ship was fired on near the eastern port of Trincomalee. A member of the monitoring team was slightly hurt.
The rebels made no immediate comment on the ruling but had earlier denied attacking the ship.
The ceasefire between the Tigers and government, in force since February, 2002, has been under growing strain.
Diving for cover
Helen Olafsdottir, spokeswoman for the Sri Lankan Monitoring Mission, said: "We have made a ruling that is that it was a violation of the ceasefire agreement. The incident undermines the spirit of the ceasefire."
The navy patrol boat was on a routine tour when the rebels shot "75 to 100 rounds of small arms fire" at it south-east of the main harbour of Trincomalee, military spokesman Daya Ratnayake said.
The ship was flying with the Sri Lanka Monitoring Mission flag indicating that monitors were on board.
The injured peace monitor was hurt while diving for cover.
Mr Ratnayake welcomed the ruling and said the rebel leadership should exercise "greater control over the regional leaders".
An increase in violent incidents this year has raised fears the three-year truce could be broken.
There have been no direct peace talks since the rebels walked out in April 2003.
The main sticking point is the amount of self-rule the Tigers should be given in the north and east of the island.
More than 60,000 people have died since the rebels began their fight for a homeland for minority Tamils in 1983.