Angry protesters halted trains and clashed with policemen in Sri Lanka's capital Friday as authorities began demolishing their homes, saying they were unauthorized constructions that encroached on government lands.

Police used tear gas to disperse the protesters who pelted stones and placed logs across a nearby rail road halting train transport for a few hours.

Opposition lawmaker Ravi Karunanayake said officials were tearing down the homes in violation of a Supreme Court stay order but were forced to stop because of the protest. He said the demolition was part of government's plans to increase security ahead of a South Asian leaders' summit starting later this month.

It was not immediately clear how clearing the land would help security, but the area is near army headquarters and an air force base.

Police spokesman Ranjith Gunasekara said although the demolition was hastened by the South Asian Association for Region Cooperation summit, occupants were given enough time to find other homes.

Gunasekara said officials had not received any court order when the demolition was carried out.

Karunanayake said officials managed to destroy about 80 homes out of 650 planned to be bulldozed.

The upcoming summit is scheduled to begin in Colombo on July 27, and the government says that it wants to ensure maximum security for visiting heads of states and officials.

Sri Lanka is fighting a 25-year civil war against Tamil Tiger rebels who want to carve out an independent state for ethnic minority Tamils in the island's north and east.

More than 70,000 people have been killed in the violence.