The Sri Lankan government plans to open two routes in the northern part of the country to allow safe passage for tens of thousands of civilians caught in the war zone.

They are being encouraged to flee along a coastal road to government-controlled areas to the north and south, Foreign Secretary Palitha Kohona said Friday.

"The idea is to ask the people to … walk away," he said. "We would hope that the LTTE (Liberation Tigers of Tamil Eelam), if they really are interested in their people, would let those people go."

Conflicting numbers on how many trapped

The government estimates 70,000 people are trapped in an area of about 50 square kilometres, though aid groups put the figure closer to 200,000.

The move did not amount to a temporary ceasefire and the government had not shelled that road in any case, Kohona said.

Meanwhile, the United Nations cautiously welcomed the move.

"Any additional measure to relieve the suffering of civilians is welcome," said UN spokesman Gordon Weiss. "Let's watch and see if this translates into an effective safe passage for trapped civilians."

UN had called for ceasefire to allow civilians to flee

The government's announcement comes on the heels of a call by UN Secretary-General Ban Ki-moon for both sides to suspend hostilities to allow civilians to flee and urgently needed aid to be delivered.

"There is an urgent need to bring this conflict to a speedy end without further loss of civilian life," UN spokeswoman Michele Montas said, speaking for Ban.

However, it's not clear how the government's announcement would alter the situation on the ground.

The rebels, who have repeatedly called for a ceasefire, could not be reached for comment due to downed communication lines.

70,000 have died in fighting

More than 70,000 people have been killed in fighting since 1983.

The rebels have been fighting for an independent state for the Tamil minority, which suffered decades of marginalization under a series of governments dominated by the Sinhalese majority.

The military has made significant inroads in recent months in driving rebels out of much of their de facto state in the north.

Many residents of the war zone said they were forced to scrounge for food after relentless shelling that killed dozens of civilians Wednesday and Thursday.

"It's been four days since my family has eaten," Mary Jacinta Balachandran, 46, told The Associated Press by telephone as she waited at a makeshift clinic in the war zone.

with files from the Associated Press