Dozens were killed and hundreds wounded when deadly clashes broke out between Tamil separatists and Sri Lankan security forces in the troubled north of the country today.

At least 52 guerrillas were killed in the battle, which the rebel group later described as a successful repulsion of a government offensive ahead of key local elections. However official military reports disputed the group's version of events, saying the army rather than the rebels had been victorious.

The defence ministry said that 38 soldiers had been killed and 84 wounded as the warring sides battled over territory on the northern Jaffna peninsula, where the Liberation Tigers of Tamil Eelam (LTTE) have established a de-facto mini-state.

A military source said that the security force casualties were 40 dead and 375 wounded, while several more remained unaccounted for.

It was the highest death toll for government forces in a single battle since October 2006, when a major Tamil counter-offensive killed 129 soldiers and wounded 515 others.

“Monitored radio communications and ground sources have confirmed that 52 LTTE terrorists have been killed and many injured in the latest skirmishes in Jaffna,” the defence ministry said.

Rasiah Ilanthirayan, a Tamil Tiger spokesman, accused the military of provoking the battle.

“They attempted to get near our positions. That’s when the clashes erupted,” he said.

The group did not report any casualty figures but pro-rebel websites claimed that they had routed security forces.

“The Sri Lankan army advanced on two fronts and the LTTE successfully thwarted their attack after 10-and-a-half hours of stiff resistance,” said Puthinam.com, a Tamil-language site.

However the military offered conflicting reports of how the battle erupted.

Brigadier Udaya Nanayakkara, a military spokesman, blamed the rebel group for sparking the violence, which he said had broken out at around 5.30 am after guerrillas overran the front lines in the Muhamalai area of the Jaffna peninsula, north of the rebels’ de facto state.

Government forces fought back with small arms, mortars and tank fire, eventually forcing the rebels to retreat and seizing 500 metres of the group’s territory, he said.

But one Sri Lankan military source appeared to confirm the rebel version of events, saying: “Troops mounted a two-pronged assault on the forward fence lines of the LTTE under the cover of darkness."

Resistance had at first been limited and the army managed to capture the guerrilla’s first line of defence, but the group eventually forced a retreat, the source said.

Jeremy Page, The Times' South Asia correspondent, said that both sides routinely inflate numbers of casualties inflicted on their opponents and underreport their own losses.

Independent accounts of the violence are unavailable because the media are barred from the war zone.

The government has vowed to dismantle the Tamil controlled region in the north and crush the group by the end of the year. It is keen to make significant military progress ahead of crucial provincial council elections across the island nation on May 10, in order to boost its poll hopes.

Today's fighting undermines official claims that having forced the Tamils out of the eastern part of the island, the group has already been virtually wiped out.

At the start of the year, the military said there were only 3,000 Tiger rebels left, yet official defence ministry figures show that 3,025 Tigers have been killed by security forces so far this year.

During the same period, the military has lost 218 soldiers, according to the ministry.

Diplomats and observers say that the government has underestimated the strength of the rebel group. Yesterday one soldier and 10 rebels were killed in separate clashes on the frontline, the military said.

The LTTE have been fighting since 1972 to carve out an independent homeland in the north and east for minority Tamils, who have been marginalised by successive governments controlled by the majority Sinhalese. Tens of thousands have died on both sides.

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