(Updates with Tiger comment, details)

By Simon Gardner

COLOMBO, May 13 (Reuters) - Gunmen shot dead a senior Buddhist monk near a border separating government from Tamil Tiger territory in Sri Lanka's northeast on Sunday, a day after troops killed five rebels, the military said.

Military spokesman Brigadier Prasad Samarasinghe said it was too early to say who was behind the monk's killing in the far northeastern district of Trincomalee, where troops have evicted the rebels from territory they held under the terms of a now tattered 2002 ceasefire.

"Two gunmen came and shot him," Samarasinghe said. "It is too early to say who has done it or even who we suspect has done it. It was in a Sinhalese area."

The Tigers denied any involvement, and pointed the finger at the state security forces.

"The monk who was attacked was a sympathiser of the Tamil cause. He had attended events in favour of the Tamil cause," Tiger military spokesman Rasiah Ilanthiraiyan said by telephone from the rebels' de facto state in the island's far north.

"The military intelligence do not want a Sinhalese monk supporting our cause so maybe they could be behind this."

Samarasinghe said the monk's shooting came a day after troops killed four Tiger fighters in the northwestern district of Mannar and another in the Jaffna peninsula.

It also came after two-dozen landmines were found on Saturday in the besieged army-held northern Jaffna peninsula, which is cut off from the rest of the island behind rebel lines.

A haul of illegal communications equipment was also intercepted while being smuggled to Tiger territory in the north.

Troops seized 30 global positioning systems and 479 communications sets hidden inside a consignment of televisions.

"The detection of all those radio sets was a major catch," Samarasinghe said.

Analysts say a new chapter in a two-decade civil war that has killed nearly 70,000 people since 1983 could be about to escalate, with the Tigers vowing to carve out an independent state in the north and east and the government pledging to destroy them militarily.

Nerves are running high in the capital Colombo after the Tigers launched a series of air raids using light aircraft smuggled into the country in pieces.

The stock exchange has slumped nearly 5 percent in a fortnight amid the uncertainty.

U.S. Assistant Secretary of State for South and Central Asian Affairs Richard Boucher visited the island this week and said Washington had suspended some aid because of concerns about abductions, killings and abuses blamed on both sides.

Britain has already suspended around $3 million in debt relief aid citing concerns over the government's human rights record and mushrooming defence spending.

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