The opposition said missiles landed near a northern airbase last week
NATO Secretary General Anders Fogh Rasmussen says Syrian government forces are continuing to fire short-range ballistic missiles at rebel fighters.
A NATO source told the Reuters news agency that surveillance had detected multiple launches of “Scud-type missiles” on Thursday morning.
Rasmussen said it was the “act of a desperate regime approaching collapse”.
Last week, NATO and the US said more than six missiles had been fired from the Damascus area into northern Syria.
However, the Syrian foreign ministry strongly denied using such weapons.
The military is believed to have access to a range of artillery rockets and medium-range missiles, some capable of carrying chemical weapons.
These include the Soviet-designed SS-21 Scarab and Scud-B missiles.
Speaking to reporters in Brussels on Friday, Rasmussen confirmed NATO and its allies had detected new launches of Scud-type missiles.
“We strongly regret that act,” he said. “I consider it an act of a desperate regime approaching collapse.”
“The fact that such missiles are used in Syria emphasises the need for effective defence and protection of our ally Turkey,” he added, referring to NATO’s decision to deploy several Patriot missile batteries along the country’s southern border with Syria.
On Thursday evening, US officials also said forces loyal to President Bashar al-Assad had resumed firing ballistic missiles against rebel positions in recent days.