War-torn Syria on Sunday advised its citizens to avoid travel to neighbouring Turkey, where massive protests have rocked several cities, because of "a deterioration in the security situation."

The warning issued by the foreign ministry comes as a civil war that has killed tens of thousands ravages Syria, pitting rebels backed by Turkey and other countries against the regime of President Bashar al-Assad.

"The foreign ministry advises Syrian citizens to avoid travel to Turkey for their own safety because of a deterioration in the security situation in a number of Turkish cities," it said in a statement carried on Syrian state television.

The warning followed the biggest anti-government demonstrations in Turkey in a decade in major cities including the capital Ankara and Istanbul. Around 1,000 people have been detained in the protests and scores wounded nationwide.

The demonstrations have been covered in minute detail by Syrian state media, and on Saturday Syria's information minister accused the Turkish government of "terrorising" its people.

Syria and Turkey were once close allies, but Ankara has parted ways with Assad over his regime's response to an uprising now in its third year.

The government of Turkish Prime Minister Recep Tayyip Erdogan has backed the rebel movement, giving shelter to hundreds of thousands of Syrian refugees, and accused Assad's regime of atrocities.

The United Nations says at least 70,000 people have been killed in the Syrian conflict since March 2011, while activists put the figure at more than 94,000.