The Syrian Democratic Forces (SDF) said in a statement on Saturday that they had captured two Daesh* militants of American nationality.

According to the statement, the SDF militants captured two Daesh terrorists, who allegedly are US citizens, Reuters reported.

The Syrian Democratic Forces (SDF) are the Kurdish-led military group backed by the US, fighting against Daesh in Syria.

Earlier on Thursday SDF issued a statement in which it vowed to ramp up attacks against Daesh positions.

"With the help of the (US-led) coalition, we will escalate our military operations to eliminate Deash remnants and chase down their sleeper cells," the SDF alliance said in a statement.

Syria has been in a state of conflict since 2011, with numerous opposition groups and terrorist organizations fighting the Syrian Arab Army in an attempt to topple the government of President Bashar Assad. Russia, along with Turkey and Iran, is one of the guarantor states of the Syrian ceasefire.

The US-led coalition of more than 70 countries is conducting military operations against Daesh (also known as the Islamic State, or IS, and banned in Russia) in Syria and Iraq. The coalition's operations in Iraq are conducted in cooperation with the Iraqi government, but those in Syria are not authorized by the Syrian government or the UN Security Council.

*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia