Iran-backed groups in Syria blew up a gas pipeline in the country's Kurdish-controlled northeast near a United States base Thursday, a war monitor said, as regional tensions grew following Israel's war with Gaza-based militants.

The attacked pipeline is near the Conoco gas facility, the Syrian Observatory for Human Rights said.

The Observatory's director Rami Abdel Rahman told Agence France-Presse the blast had gone off close to a US base.

Flames rose from the site of the explosion, the British-based monitor with a large network of sources inside Syria reported. But it said there had been no casualties.

On Wednesday, the US Central Command said it had shot down two drones and damaged a third in Iraq over the past 24 hours, with allied troops suffering "minor injuries" in one incident.

It did not say who launched the drones, but pro-Iranian groups have threatened to attack American troops in Iraq because of Washington's support for Israel in its war with Hamas.