NATO voiced concern Tuesday that Russia's air attacks in Syria creates the risk of "an incident getting out of control," as Moscow and the US-led international coalition pursue different military objectives in the country.

"It's clear that Russian objectives and their air operations over Syria and those of the anti-ISIL (Islamic State) coalition are not the same," said NATO Deputy Secretary General Alexander Vershbow.

"So that does increase the risks of an incident getting out of control," he told reporters in Lisbon on the margins of a defence industry forum.

Moscow began air strikes in Syria last month in cooperation with the government in Damascus and says it is targeting the Islamic State group and other "terrorists".

But the United States -- which is leading a separate bombing campaign in coordination with other Western and Middle Eastern states -- has accused Russia of chiefly targeting moderate rebel groups battling President Bashar al-Assad.

Russian air strikes in Syria have killed 370 people since they began on September 30, around a third of them civilians, a monitoring group said Tuesday.

The Syrian Observatory for Human Rights said 243 rebel fighters had been killed, among them 52 from the Islamic State group, along with 127 civilians.

Vershbow said NATO members would be discussing in the weeks ahead "whether there is any additional measures or precautions that allies should take to ensure that there's no challenge to the integrity of the Turkish borders."

NATO member Turkey has bridled at Russia's efforts to prop up the Assad regime.

The country has accused Russian aircraft operating in Syria of violating its air space twice, with Moscow blaming poor weather.

A drone downed by Turkey near the Syrian border was Russian-made, Turkey's prime minister said Monday, adding that it could have belonged to one of Syria's various armed groups.

Earlier this month, NATO Secretary General Jens Stoltenberg warned that the alliance was ready to deploy forces in key member Turkey if needed after Ankara complained about the Russian overflights.

From October 3-6 NATO held its biggest military exercise since 2002, putting 36,000 alliance soldiers through their paces in Italy, Spain and Portugal to boost preparedness against the backdrop of the Ukraine crisis in which Russia is accused by the West of playing a leading role.

Any "potential aggressor should take note of the capabilities and the readiness that we're demonstrating," said Vershbow.

While he added that the exercises weren't aimed at any particular country, the West's ties with Russia have been strained over both Syria and Moscow's role in the crisis in Ukraine.