Russia has resumed bombing moderate opposition fighters in Syria, a U.S. military officer from Baghdad told reporters at the Pentagon Tuesday.

"We have seen them begin operations again in that region," Air Force Maj. Gen. Peter Gersten, the U.S.-led coalition's deputy commander for operations and intelligence, told Fox News.

President Obama called Russian President Vladimir Putin last week asking him to help "press" Syria to end its airstrikes, according to a White House statement. The strikes appeared to violate the ceasefire brokered by the United States and Russia in February.

"The two leaders committed to intensify their efforts to shore up the Cessation of Hostilities and affirmed the need to end attacks by all parties," the statement read.

Fox News has learned Russia also restarted airstrikes against Syrian opposition fighters, some backed by the United States.

Russia claims it is striking Jabhat al-Nusra, otherwise known as the al-Nusra Front, Al Qaeda's Syrian affiliate. The group is not bound to the ceasefire agreement.

The "cessation of hostilities" has shown signs of fraying as the Syrian regime resumed bombing operations in northwest Aleppo and in the coastal province of Latakia where a Russian airbase is located. Russia claims al-Nusra is trying to take over Aleppo and parts of Latakia province.

Moscow has urged the United States to share targeting information on Nusra.  So far the United States military has refused to cooperate.

"We only see them, we don't actually coordinate in any way with them," Gersten said, referring to the Russian Air Force operating in Syria.

Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel. You can follow him on Twitter: @LucasFoxNews