Sri Lanka's Tamil Tiger rebels have accused the army of killing 129 people by opening fire into a designated safe zone where civilians are trapped.

The rebels say the army shelled a no-fire zone in the country's northeast Wednesday in what the separatist fighters called the "most cruel carnage."

The government denies the allegations, and the accounts cannot be independently verified.

Sri Lanka's military says it is on the verge of defeating the rebels who have been fighting since 1983 for a separate homeland for ethnic Tamils.

The United Nations says U.N. Secretary-General Ban Ki-moon reiterated his concern for tens of thousands of civilians trapped in the conflict zone, during a phone conversation with Sri Lankan President Mahinda Rajapaksa on Thursday.

The U.N. issued a statement saying Mr. Ban reminds all sides of their obligations to protect civilians, and stresses that civilians should be allowed to leave the affected areas.

A months-long military campaign has cornered the Tamil Tigers in a narrow strip of land in the country's north.  The U.N. says there are more than 100,000 civilians cornered along with the fighters.