Russian military planes filled with humanitarian aid landed in Syria on Saturday, Russia’s Defense Ministry said, just days after officials from the U.S. and NATO warned Moscow against furthering its military support of the government of Syrian President Bashar Assad.

Russia sent 80 tons of supplies to a military base in the coastal city of Latakia, according to Syrian state media. The aid is capable of supporting more than 1,000 refugees, AP reports. Maj. Gen. Igor Konashenkov of Russia’s Defense Ministry said the planes were packed with camp materials such as beds, cooking equipment and food.

The Syrian National Coalition, an organization of opposition forces, criticized the move as a “direct Russian military intervention,” AP reports. The coalition warned that Russia’s action is an attempt to meddle in Syrian affairs and represents a creeping occupation of the country.

The aid comes as Russia also boosts its military presence in Syria, in direct conflict with the wishes of Assad's adversaries. Russia has been a longtime supporter of his administration, while the U.S. has called for Assad’s removal.

The Russian government has repeatedly sent weapons and soldiers to Syria, BBC reports, and conducted training exercises with members of the Syrian Army. Between 2009 and 2011, Russia’s government provided about 71 percent of the military equipment deployed by Syria’s government. 

On Friday, Russian Foreign Minister Sergei Lavrov said Moscow intended to continue these efforts despite opposition from the U.S. and NATO, Al Jazeera reports. He refused to comment on whether Russian soldiers were actively fighting in Syria. 

U.S. President Barack Obama has voiced his concern that Russia would continue to grow its support as rebel groups make inroads on government-held territory. Following Lavrov’s statement Friday, he reiterated those concerns and called Russia’s strategy of empowering Assad through military and humanitarian aid “a big mistake” and “doomed to fail.” 

Assad's administration has repeatedly launched attacks on its own citizens in an effort to stifle opposition and beat back Islamist militant groups ISIS and Hezbollah. A continuing civil war between these factions has killed at least 240,000 people and caused millions more to flee the country and seek asylum throughout Europe.