Myanmar ? Myanmar’s junta arrested prominent political activists Saturday, Amnesty International said, including one who went into hiding after leading some of the first major marches against the government several weeks ago.

The United Nations has called on the military government to halt its crackdown on the protesters, and a U.N. special envoy was expected in the region today to help coordinate a response among key Asian governments.

Among those detained Saturday was Htay Kywe, who led some of the first marches several weeks ago before going into hiding to escape a government manhunt, Amnesty said. Others arrested were Aung Htoo and Thin Thin Aye, also known as Mie Mie.

The three were believed to be the last remaining activists at large from the 88 Generation Students’ Group – the country’s boldest dissident group – which was at the forefront of a 1988 democracy uprising and one of the main forces behind the protests that started in August.