U.S. warplanes hit the ISIS stronghold of Sirte in Libya in support of the Tripoli government’s efforts to retake the port city, the Pentagon said Monday.

The airstrikes were authorized by President Barack Obama on the recommendation of Defense Secretary Ashton Carter and Joint Chiefs Chairman Marine Gen. Joseph Dunford, Pentagon Press Secretary Peter Cook said in a statement.

The release didn’t describe the duration of the strikes, the type of aircraft used or whether they were land- or carrier-based.

The airstrikes were requested by the Libyan Government of National Accord, which is based in Tripoli and is supported by the United Nations, according to the statement. The strikes were aimed at defeating ISIS “in its primary stronghold in Libya,” it said.