The Syrian military has fired a ballistic missile towards cities in the north, Nato says, making it the third such launch in recent days.
The BBC understands that the missiles were unguided and were fired in the direction of Aleppo and Idlib.
Nato is currently deploying Patriot anti-missile batteries along Turkey's border with Syria.
In another development, Syria has denounced UN and Arab League envoy Lakhdar Brahimi as "flagrantly biased".
The foreign ministry statement came after Mr Brahimi said a speech by Syrian President Bashar al-Assad on Sunday was a "lost opportunity" to resolve the crisis.
"Syria is shocked by the statements of Lakhdar Brahimi, who has overstepped his mandate and exhibited a flagrant bias for those parties known to be conspiring against Syria and its people," the televised statement said.
A Nato spokeswoman said they had detected the launch of a ballistic missile inside Syria on Wednesday, following similar launches last week.
The BBC understands that the targets appeared to be key road junctions and former government bases overrun by rebels.
Scuds are in the Syrian military's armoury, but Nato could not confirm the type of missile used. The Syrian government has previously denied using ballistic missiles.
The BBC's diplomatic correspondent Jonathan Marcus says that, for Nato, the move will underscore the importance of using Patriots to defend Turkish airspace.
US batteries could be operational within the next few days, but Dutch and German batteries may not be in place for some weeks.
Last month, Nato condemned the use of ballistic missiles saying it showed "utter disregard" for the Syrian people.
Rebel forces have gained control of swathes of northern Syria in recent months and Aleppo is largely under rebel control.
The UN estimates that more than 60,000 people have been killed in the Syrian uprising, which began in March 2011.