A powerful blast hit Manbij, the northern Syrian city recently threatened by Turkey over the Kurdish control.
Several people were killed, with local sources claiming US soldiers allied with the Kurds were among the victims.
Blackhawks are reportedly landing next to the targetted site in Manjib while
US Servicemen were injured.
A US patrol was near the targeted restaurant – according to locals, some were enjoying a meal inside the restaurant.
Al Jazeera source claimed that six civilians were killed and 19 injured in downtown Manjib, Syria as a result of a blast that coincided with US forces patrol in the city centre.
The Syrian Observatory for Human Rights (SOHR) said US-backed coalition forces were the intended target but did not specify whether those killed were soldiers or civilians.
Manbij Military Council spokesman, Shervan Dervish, confirmed the explosion took place on Wednesday afternoon.
It is not yet known who or what caused the explosion.