A Saudi government source revealed on Thursday that Gulf Arab countries have ramped up their supply of weapons to Syrian rebel groups in response to Russia’s escalating military support of President Bashar al-Assad, adding yet another layer of complexity to the four-year old war.

The unnamed official told the BBC that the groups receiving aid were not affiliated with the Islamic State in Iraq and the Levant (ISIL), but included Western-backed groups such as the Free Syrian Army, as well as Jaysh al-Fatah, which has ties to the Al-Qaeda-affiliated Nusra Front.

Russia launched its airstrike campaign last week with the declared purpose of combating ISIL, which has wrestled control of large swathes of Syria from the Assad regime. However, Russia’s military has since targeted a broad range of anti-Assad Syrian rebel groups, including those now reportedly being sent increased military aid from the Gulf.

While Gulf states and Russia are both opposed to ISIL, they are at odds over the future role of Assad and non-ISIL Syrian rebel groups in any post-civil war Syria. Saudi Arabia and its allies have long supported those groups trying to overthrow Assad, while Russia sees little differentiation with most of the Syrian rebel groups who want to unseat Moscow’s longtime ally.

Russia’s military campaign in Syria, which Moscow officials have said could last up to three or four months, “will almost certainly provoke counter-escalation by regional states – namely Saudi Arabia, Turkey and Qatar – who remain absolutely committed to ensuring Assad's demise,” wrote Julien Barnes-Dacey, a Middle East expert at the European Council on Foreign Relations, earlier this week, before the report of an increased flow of arms.

The Russian intervention appears to have frozen what some analysts saw as a budding rapprochement between Moscow and Saudi Arabia – the leading Gulf Arab power – over the Syria conflict.

The United States, Russia and Saudi Arabia participated in a rare trilateral summit in Doha in August. The meeting raised hopes of a new diplomatic effort to end the war, which since 2011 has claimed more than 250,000 lives and resulted in more than 7.5 million people fleeing their homes.

But any diplomatic openings have for the moment been overtaken by the uptick in violence since Russia's increased role in the conflict.

On Thursday, Syrian government forces supported by new Russian airstrikes continued a major ground offensive in the country’s west, a day after Moscow fired cruise missiles into Syria from hundreds of miles away in the Caspian Sea.

Meanwhile, Turkey has become increasingly incensed at purported Russian violations of its airspace during Moscow’s flight missions in Syria. Ankara has summoned Russia’s ambassador to Turkey three times this week over the incidences, which NATO called “extremely dangerous.”

NATO said Thursday that it was prepared to send troops to Ankara to defend the NATO member in response the airspace violations, a largely symbolic announcement that nonetheless underscored the regional repercussions of the ongoing Syrian conflict.

The U.S. has also reacted negatively to Russia's military intervention in Syria, saying its actions there would likely exacerbate violence and extremism in the country. The U.S. military, which continues to conduct airstrikes in Syria as part of its international coalition against ISIL, has refused to coordinate with Moscow, although channels aimed at ensuring that U.S. and Russian planes avoid collisions have been discussed.