Amid an upsurge in violence in the island nation, Sri Lankan security forces on Saturday cordoned off several areas of the capital Colombo for a surprise house-to-house hunt for suspected Tiger rebels, residents and defence officials said.

The pre-dawn operation was concentrated in Colombo's Wellawatte region where minority Tamils live in larger numbers, residents said.

They said they were not allowed to step out of their homes for several hours.

Soldiers at entry points to the area announced that a curfew had been declared and no one was allowed to enter or leave the area until the search was completed.

Defence ministry spokesman Prasad Samarasinghe denied that a curfew had been imposed.

There was no immediate indication of arrests.

The search operations came amid an escalation in violence in the island's north-east where at least 50 security personnel and 35 others had been killed in clashes linked to the country's drawn out Tamil separatist conflict.