BEIRUT — Syrian insurgents and opposition activists said Monday that rebel forces had taken control of Syria’s largest hydroelectric dam, an assertion that, if confirmed, would give them significant control over a vital reservoir and what remains of the sporadic power supplies in their war-ravaged country.
The Tabqa Dam, built more than 40 years ago with Russian help on the Euphrates River in northeast Syria’s Raqqa province, provides electricity to areas that are both in rebel and loyalist hands, including the contested city of Aleppo. It would be the third Euphrates dam taken by the rebels, who control two smaller facilities upriver.
But the Tabqa Dam, which the government once boasted had made Syria self-sufficient in power generation, is considered a more potent weapon in the battle for allegiances in the nearly two-year-old Syria conflict. Rebel-held areas have been systematically denied electricity by President Bashar Assad’s forces in their effort to turn the population against the insurgency.
Claims that the Tabqa Dam was in rebel control came as a possible new confrontation was brewing between Turkey and Syria after a Syrian minivan exploded just inside Turkish territory at Cilvegozu, an important border crossing near the rebel-held Syrian town of Bab al-Hawa, killing at least 13 people, including three Turkish civilians, wounding at least 28, and damaging at least 19 vehicles.
The Turkish fatalities were believed to be the first related to the Syrian conflict since October, when a Syrian mortar shell killed five Turks near the border-crossing town of Akcakale, Turkey, eliciting a warning of retaliation by the Turkish government.
Turkey’s deputy prime minister, Bulent Arinc, did not rule out a bombing or suicide attack as the cause of the Cilvegozu explosion and said all possibilities were under investigation at the border post in southern Turkey’s Hatay province.
Syrian rebels, who get military and financial support from Turkey, blamed Assad’s government for the explosion. Turkey, which hosts nearly 200,000 Syrian refugees, has repeatedly warned Assad’s government it would not tolerate attacks along the 550-mile border.
Reports by rebel commanders and by the Syrian Observatory for Human Rights, an opposition group based in Britain with a network of contacts in Syria, said insurgents had met little resistance as they swept into the Tabqa area Sunday, seizing the dam and setting fire to an imposing statue of Assad’s father and predecessor, Hafez, in the city of Tabqa.
The reservoir created by the dam, known as Lake Assad, is Syria’s largest and is vital for irrigating farms and supplying drinking water to Aleppo.
The Syrian government did not confirm the insurgent claims. But videos uploaded on the Internet by insurgents appeared to corroborate they were in control of areas inside and outside the dam, although not necessarily the control room. One rebel was quoted as saying the insurgents intended to divert power from the dam to rebel-held areas.
He said that rebels also had taken control of large areas of Tabqa, including a military police barracks, an air force facility, and an artillery base, seizing weapons and ammunition, and that they did not intend to damage any infrastructure.
‘‘The Shabiha says, ‘Assad or burn the country,’’’ he said, using the term for the feared plainclothes pro-government militias. ‘‘We say, ‘We will burn Assad and keep the country.’’’
Fighters in the operation included members of the Al Nusra Front, the Islamic militant group that has developed a reputation for its fearless attacks on Assad’s military but has emerged as a problem for the United States, which wants to aid the Syrian insurgency but considers Al Nusra a terrorist organization with ties to Al Qaeda in Iraq.