The rebel Free Syrian Army said on Friday that Syrian troops were massing near the Turkish border amid tensions since Syria's downing of a Turkish jet last week.
"There are military units massing 15 kilometres or slightly more (10 miles), from the Turkish border, in the northern region" of Syria, FSA supreme military council head Mustafa al-Sheikh told AFP by telephone.
Asked to comment, a Syrian foreign ministry spokesman reported: "No hostile intentions from the Syrian side."
Sheikh said that around 2,500 troops backed by 170 tanks and other vehicles were stationed in the border area, roughly 25 kilometres (15 miles) from the main northern city of Aleppo, citing estimates from fighters on the ground.
Government forces have "regrouped and withdrawn from some of their checkpoints on the outskirts of Aleppo city to new locations" near the border, he said.
Sheikh said the troop build-up could be a "show of force against the Turkish military, which increased its presence on the Syrian border after the downing of its warplane by Syria."
"Fearing Turkish military intervention, the Syrian military proceeded to mobilise its forces," he said.
But he said the troop concentration might equally be in preparation for an operation inside Syria following heavy bombardment of the area by government forces in recent weeks.
"Another possibility for this mobilisation may be a crackdown in the northern Aleppo countryside," he said.
Turkey has sent missile batteries, tanks and troops to the border as a "security corridor" after Syria shot down a Turkish warplane late last week, media reports said.
State-run TRT television showed dozens of military vehicles reportedly heading for the border, in a convoy that included air defence systems.
The Turkish Phantom F-4 jet was downed by Syria over the eastern Mediterranean in what Prime Minister Recep Tayyip Erdogan called a "heinous attack" over international waters.