Thai riot police scuffled with demonstrators barricaded inside the prime minister's compound on Friday as they delivered an eviction order against the group seeking to oust the government.

Armed with batons and shields, police posted the court order on lampposts and the iron gates of the compound, scene of a four-day occupation by the People's Alliance for Democracy (PAD) that has sparked fears of major violence and rattled investors.

Police briefly detained at least 15 protesters and took up positions around the PAD-controlled area, but they did not move to evict the 4,000-strong crowd inside. Police spokesman Surapol Thuanthong told reporters they only intended to help court officials deliver the eviction order.

"We are trying to deal with the protesters as gently as possible. We are persuading them to leave the compound and will not do anything to those who follow the court order," he said.

The PAD urged more supporters to gather at the compound until the current elected administration fell.

"Move in and circle around me. We can't let them seize our stage too easily," retired general and PAD leader Chamlong Srimuang told the cheering crowd from atop the rock concert-like like platform that now sits on the Prime Minister's front lawn.

Nine PAD leaders have been charged with insurrection, a crime that can carry the death penalty, after violent raids on government offices and a state TV station on Monday, which some newspapers criticised for going too far.