The US military denied there was any attack. "There is no truth to the reports that US forces in Syria were attacked by rockets today," tweeted coalition spokesman Col Wayne Marotto.
Earlier Sunday, Siyamend Ali, a spokesman for the US-backed and Kurdish-led Syrian Democratic Forces, said two rockets were fired at the al-Omar field in Syria's eastern province of Deir el-Zour without inflicting any casualties. He added that it was not immediately clear where the rockets were fired from.
The Britain-based Syrian Observatory for Human Rights said the rockets were fired from an area in Mayadeen, also in Deir el-Zour. Syria's state news agency, SANA, also reported that the al-Omar facility was hit with two rockets.
Later Sunday, the Syrian Democratic Forces denied reports that another base housing US troops was hit, saying the sounds of explosions at the facility, known as Conoco, were from training with live ammunition.
The rocket attack on al-Omar came six days after US troops in eastern Syria came under a similar attack. Last week's attack came a day after US Air Force planes carried out airstrikes near the Iraq-Syria border.