"Hamid Suleiman Mohammed and Adnan Muwaymesh were jailed for 10 years and Ibrahim Haj Yussef and Ahmed Hassan Habash for seven," the National Organisation for Human Rights in Syria said in a statement.

The state security court convicted the four of "seeking through their actions, plans or writings to break away areas of Syrian territory so that they can be annexed to an independent state."

The four were arrested in March 2006 after taking part in a demonstration in the town of Afrin, north of Syria's second city of Aleppo, on the eve of celebrations for the Kurdish new year holiday of Nowruz.

They were originally accused of attacking a security force patrol in the town, which lies in the heavily Kurdish region of Kurd Dagh, the rights group said.

The state security court also sentenced two suspected Sunni Islamists to two-year jail terms for "inciting communal and ethnic tensions."

Both Hassan al-Jabiri and Abdel Razzaq Trabulsi were released on time served, the watchdog said.

The use of the state security court to try dissidents has drawn repeated criticism from Syrian human rights groups.

Established under the country's 45-year-old state of emergency, the court's judgements are final and cannot be appealed.

The Syrian League for the Defence of Human Rights called on the authorities to get rid of the court and "end the problem of political prisoners by releasing all of them."