The death toll in U.S. air strikes on pro-Iran installations in eastern Syria has risen to 19 fighters, the Syrian Observatory for Human Rights, a war monitor, said on Saturday.

The observatory said that toll was from the initial U.S. response to a drone attack on Thursday on a U.S. military position in Syria that killed one American contractor and wounded another contractor and five troops.

Reuters was unable to independently confirm the toll.

  - Reuters