The Syrian Democratic Forces (SDF) backed by the US reportedly gained control of Tabqa military airport, which was held by the Islamic State (Isis), near Raqqa on Sunday (26 March).
The development is viewed as an important step in the battle against the jihadists, who declared Raqqa as their de-facto capital in 2014.
The Syrian alliance of Kurdish and Arab militias with the support of US special forces have ousted Isis militants from large parts of northern Syria. SDF fights separately from other rebel groups who seek to overthrow President Bashar al-Assad.
The SDF have been waging a battle against the Isis jihadists near the Tabqa damn and the airbase.
Meanwhile, as the coalition air strikes accelerated in the last few days hundreds of civilians and families fled the city of Tabqa to safer areas, Reuters news agency reported.
The Britain based Syrian Observatory for Human rights said that at least 90 people were killed in the latest campaign of coalition air strikes on Tabqa and western countryside of Raqqa province.
Last week, the Pentagon said that it had airlifted local ground forces to place them behind Isis front lines in a move to capture the Tabqa dam.
Isis on its social media channels had earlier warned that the Tabqa dam could collapse and raised fears of flooding. The dam, however, appears intact, the BBC reported.
There were conflicting reports of damage to the dam on Sunday, (26 March) as civilians allegedly fled to higher ground. The jihadist group later sent its people around Raqqa saying that the dam was intact and they did not have to flee.
SDF spokesperson Silo rejected claims that coalition air raids hit the dam's structure. "The capture of the dam is being conducted slowly and carefully and this is why the liberation of the dam needs more time."
The strategically significant dam provides electricity to the area and is about 4.5km long. The complex of the dam is also used by the militants to plot attacks outside Syria, the Pentagon said.