Russian President Vladimir Putin
Russian President Vladimir PutinReuters

Russia has moved its first fighter jets to a growing base in Syria, defense officials said Friday, according to The Wall Street Journal, raising new concerns Moscow is preparing to play a direct role in helping embattled President Bashar Al-Assad against Islamic State (ISIS) militants.

Defense officials said at least four tactical fighter jets had arrived at the rapidly expanding airfield on the Syrian coast south of Latakia.

Over the past two weeks, defense officials added, Russia has dramatically stepped up development of the airfield by sending in housing for up to 2,000 people, attack helicopters, choppers to transport troops around the country, and artillery.

The arrival of the jet fighters is the most concerning development for the U.S., which regularly flies surveillance flights and airstrikes against ISIS forces in Syria.

Defense officials said they weren’t certain how Russia planned to use the jets, but noted that the Soviet planes are designed for air-to-air combat.

The move follows several reports that Russia had sent a military advance team to Syria and had been increasing its military presence in the war-torn country.

The arrival of the jets was first detected Friday, hours before Defense Secretary Ashton Carter spoke to Russian Defense Minister Sergei Shoygu about Russia’s deepening role in Syria. The call marks the first time the two men have spoken this year, noted The Wall Street Journal.

During their 50-minute call, Shoygu told the Pentagon chief that Russia’s military buildup in Syria is “defensive in nature,” according to a senior U.S. defense official.

The moves “were designed to honor commitments made to the Syrian government,” the official said.

Defense officials said the two leaders discussed the need to prevent a conflict between Russian forces in Syria and the U.S.-led coalition carrying out regular intelligence flights and airstrikes in the country.

The Defense Department described the call as constructive and said the two leaders agreed to keep the channel of communication open.

The United States was so concerned about reports of Russia’s increased presence in Syria that Secretary of State John Kerry phoned his Russian counterpart Sergei Lavrov a total of three times in ten days to discuss the situation.

The Russian government said on Thursday its military support for Damascus was aimed at fighting terrorism, safeguarding Syria's statehood and preventing a "total catastrophe" in the region.

Lavrov reiterated earlier this week that Russia will support the Syrian government in the fight against ISIS, saying that excluding the Syrian army from the fight against ISIS is “absurd”.

Meanwhile, a Syrian military source revealed earlier Thursday that Assad's regime has in recent weeks begun using advanced air and ground weapons from Russia.

The source told Reuters that the new weapons feature high efficiency and accuracy, and that Assad's army trained on them for several months before their recent deployment on the battlefield.

(Arutz Sheva’s North American desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Arutz Sheva articles, however, is Israeli time.)