US forces in eastern Syria took indirect fire on Saturday but initial reports indicated there were no casualties or damage, a US defence official told Reuters. Hours later, another attack at Coalition forces stationed at the Al Omar oil field was also launched, a UK-based monitoring group reported.
The incidents are the latest in a series of attacks on US personnel in Iraq and Syria in recent days.
The official said the attack occurred in Conoco, Syria near Deir Ezzor where oil and gas fields are present and US troops are deployed.
The US backs Kurdish groups, known as the Syrian Democratic Forces (SDF), to operate and protect these oil fields and fight ISIS in Syria's eastern region.
There are a total of about 900 US troops in Syria.
A spokesman for US Operation Inherent Resolve, the multinational effort against ISIS in Iraq and Syria, did not immediately comment on the incidents.
Last week, unidentified sources also attacked the Al Omar oilfield in eastern Syria, the SDF reported.
US diplomats and troops in Iraq and Syria were targeted in three rocket and drone attacks on Wednesday alone, including at least 14 rockets hitting an Iraqi airbase hosting US forces, wounding two American service members.
On Thursday another attack targeted the heavily fortified Green Zone which houses the US Embassy in the Iraqi capital.
While there have not been immediate claims of responsibility for the attacks, analysts believed they were part of a campaign by Iran-backed militias.
Iraqi militia groups aligned with Iran vowed to retaliate after US strikes on the Iraqi-Syrian border killed four of their members last month.
Commander of the Kataib Sayyid Al Shuhada group, Abu Alaa Al Walae, told the Associated Press in an interview that he would conduct operations to take "revenge on the Americans".
Iran has denied supporting attacks on US forces in Iraq and Syria and condemned US air strikes on Iran-backed groups.
US forces, who have 2,500 troops deployed in Iraq as part of an international anti-ISIS coalition, have been targeted almost 50 times this year in the country.
The US has been holding indirect talks with Iran aimed at bringing both nations back into compliance with the 2015 Iran nuclear deal, which was abandoned by the Trump administration. No date has been set for the next round of the talks, which adjourned on June 20.