BEIRUT — Fresh from declaring that they had seized an important military airport and an air defense base just outside Damascus, Syrian rebels on Monday said they overran a hydroelectric dam in the north of the country.
It is the latest in a monthlong string of tactical successes that demonstrate the rebels’ ability to erode the government’s dominance in the face of withering aerial attacks. The dam supplies electricity to several parts of Syria, the activists said, and lies on an axis between the northern provinces of Raqa and Aleppo, apparently broadening the rebels’ potential supply lines in northern Syria.
The rebels said they also seized hand grenades and rocket-propelled grenades at the Tishrin Dam, which is on the banks of the Euphrates River near the town of Manbij. While the rebels called capture a strategic victory, it was not clear whether they were able to operate the dam or to withstand a government counterattack.
On Monday, the Syrian war was reported to have spilled beyond the country’s border, drawing in Turkish antiaircraft gunners who were said by the insurgents to have opened fire on a government warplane that appeared to have entered Turkish airspace as it attacked rebel positions in the Syrian town of Atma, just across the Turkish-Syrian border.
According to two antigovernment Syrian opposition groups — the Syrian Observatory for Human Rights and the Local Coordinating Committees — and a fighter on the ground, who gave his name only as Saado, the Turkish fire deterred an attack on an area that includes a rebel headquarters and a camp for displaced Syrians.
But there was no confirmation of the episode from Turkey, and the Syrian state news agency did not refer to the rebels’ claims. Government warplanes also attacked the Bab al-Hawa border crossing at the Turkish border, an area where rebels have had control for several months, according to an antigovernment activist in Turkey.
Many displaced Syrians have taken refuge in the area and fled in terror from the fighting, said the activist, who gave his name as Abu Zaki. The attack showed the government’s ability to strike at will from the air even in rebel-held territory where it has no control on the ground.
Syria and Turkey have exchanged mortar fire on numerous occasions in recent months, and Turkey, a NATO member, has requested that the alliance provide it with Patriot antimissile batteries, a possible step toward creating a de facto no-fly zone in northern Syria to protect rebels from Syrian government air attacks. Turkey has come under criticism from Russia and others for the request.
On Monday, Turkey’s military insisted that the Patriot missiles would be used only to defend Turkish territory.
‘‘Deployment of air and missile defense systems is a measure solely against potential air and missile threats that might come from Syria,’’ said a statement posted on the Turkish army’s website. ‘‘It is out of question for it to be used either for a ‘no fly zone’ or an offensive operation.’’
A group of NATO officials was expected to start assessing Turkey’s southern border with Syria to identify sites for possible bases, and determine staffing and other technical details. The foreign troops that would accompany the Patriot systems would be subject to a special agreement, the statement said.
Rebel forces had been besieging the Tishrin Dam’s defenses for days. On Monday, amateur video, which could not be verified, showed what purported to be rebel soldiers ransacking boxes of weapons captured after the raid on the dam.
“Here are your spoils, Bashar,’’ a voice can be heard saying, referring to President Bashar Assad. ‘‘Here are your weapons, Bashar. God is great,’’ a rebel exclaims as two men are filmed carrying off a trunk of munitions.
The British-based Syrian Observatory for Human Rights, which compiles its reports from militants on the ground, said the rebels overran the facility before dawn.
Over the past month, rebels have seized or damaged major military bases, making off with armored vehicles, antiaircraft weapons, and other equipment they need to break the stalemate in the grinding conflict, which has taken more than 30,000 lives. But they have not tried to hold all of the bases, as they become easy targets for government airstrikes.