The deployment in the north-eastern port district on Wednesday comes a day after a mine blast against a navy bus on Tuesday which wounded 12 sailors and sparked the withdrawal of the monitors, a military official said. The government suspects Tamil Tiger rebels of carrying out the attack.
A military official said: "With no monitoring of the ceasefire any more in Trincomalee, we think it leaves the door wide open for the Tigers to escalate attacks."
The Norwegian-led Sri Lanka Monitoring Mission (SLMM) said its first suspension of work in an entire district followed an escalation of violence that culminated in Tuesday's incident.
In a statement, the mission said: "The SLMM has decided to suspend operational activities in Trincomalee until further notice."
It added that it planned to resume normal monitoring activities as soon as the situation calmed down.
"The SLMM has decided to suspend operational activities in Trincomalee until further notice"
A mission statement
The SLMM was targeted earlier this month in a bomb attack in neighbouring Batticaloa district, which has also seen deadly attacks and assassinations.
On Tuesday, the UN urged Colombo and the Tigers to resume stalled talks and said a return to war was not the answer. The conflict between majority Sinhalese and minority Tamils has claimed more than 60,000 lives since 1972.
Norway sent Hans Brattskar, its ambassador to Sri Lanka, to the rebel-held town of Kilinochchi on Tuesday for talks with the LTTE leadership on salvaging the ceasefire arranged by Oslo that has been in place since February 2002.
Brattskar was accompanied by members of the SLMM who later announced the suspension of their work in Trincomalee.
More attacks feared
The LTTE said it had discussed with Brattskar the need to disarm members of a breakaway rebel faction allegedly backed by Colombo, a reduction of violence and an end to what it called harassment by security forces.
They also discussed arrangements for a visit early next week by Erik Solheim, the Norwegian international development minister, who will try to jump-start peace talks that have been on hold since April 2003.
LTTE accuses the security forces
of harassing its members
The pro-rebel Tamilnet reported that Anton Balasingham, the LTTE's London-based chief negotiator, would return to the island next week to join talks with Solheim.
Tamilnet quoted Balasingham as saying: "What is of critical importance at this crucial juncture is to try and bring an end to the brutal violence perpetrated against innocent Tamil civilians and create a congenial environment conducive for positive engagement."
Diplomatic and defence sources say they fear more attacks in the run-up to Solheim's visit as the Tigers try to collect bargaining chips by scoring more hits on the security forces.