The U.N. envoy to Iraq is warning that the violence in Iraq can no longer be separated from the civil war in neighboring Syria because "the battlefields are merging."

Martin Kobler told the U.N. Security Council on Tuesday that "Iraqi armed groups have an increasingly active presence in Syria."

As a result, he said, the Syrian conflict isn't just spilling over into Iraq.

"Instead, the conflict has spread to Iraq, as Iraqis are reportedly taking arms against each other in Syria, and in Iraq," Kobler said.

He warned that the violence "could easily spiral out of control if not urgently addressed."

Kobler said the last four months have been among the bloodiest in Iraq in the last five years with nearly 3,000 people killed and over 7,000 injured.