Iran Press/Middle East: US service members were killed in the attack, according to a tweet from the spokesperson for the US-led coalition Operation Inherent Resolve.
"US service members were killed during an explosion while conducting a routine patrol in Syria today. We are still gathering information and will share additional details at a later time," the tweet said.
The coalition has not said how many service members were killed. Prior to Wednesday's attack, only two US service members had been killed in action in Syria since the start of the campaign in 2014, CBS News reported.
The attack comes less than a month after US president Donald Trump announced that US troops would withdraw from Syria.
Trump first said the withdrawal would be underway within a month. US State Department officials put the timeline at 60 to 100 days.
The US deployed troops and equipment to Syria in 2014 as part of a Washington-led coalition supposedly fighting the ISIS terrorist group.
The US government openly sought to topple Syria's government, which had supported popular resistance against Israel.
The Syrian Arab Army has increasingly liberated occupied territories from foreign-backed terrorist groups, such as ISIS in recent years.
Manbij lies 30 km south of the Turkish border, in Aleppo province. 101/ 211 / 202
Read More:
Turkish-backed terrorists withdraw from areas surrounding Manbij
Iran welcomes entry of Syrian government forces into northern town of Manbij
