BEIRUT: Rebels captured a military air base near Aleppo on Tuesday and stormed another that protects the city's international airport, their second straight day of major strategic conquests, activists said.
On Monday, opposition fighters seized the nation's largest dam, an iconic industrial symbol of the four-decade rule of President Bashar Assad's family.
In New York, U.N. human rights chief Navi Pillay said the death toll in Syria's civil war is probably approaching 70,000, up from an estimate of more than 60,000 made less than six weeks ago.
Pillay said the U.N. Security Council's deep division and inaction over the nearly 2-year-old conflict "has been disastrous and civilians on all sides have paid the price."
The director of the Britain-based Syrian Observatory for Human Rights, Rami Abdul-Rahman, said that after days of sporadic clashes around the Jarrah airfield in Aleppo province, rebels launched a major assault on the base on Monday. By Tuesday, they had overrun it.
He said several regime troops in the area were killed or wounded in the fighting, while others fled as the rebels advanced. There was no word on opposition casualties.
The airfield, which is located near the Furat dam captured on Monday, housed fighter jets used in airstrikes on rebel held-areas.
A video posted online by activists showed several military aircraft at Jarrah. Some were parked on the tarmac while one was in a hanger with boxes of ammunition piled up against a nearby wall.
"These warplanes are now in the hands of Ahrar al-Sham Islamic movement," one fighter says in the video, referring to a rebel unit.
The video appeared genuine and corresponds to other Associated Press reporting on the events depicted.
The air base is located near the northeastern town once known as Tabqa. The town's name changed to Thawra, Arabic for revolution, after the Furat dam was built there in the late 1960s.
Earlier this month, the Observatory said rebels seized another smaller dam in Raqqa province, the Baath dam, named after Syria's ruling party.
In November, Syrian opposition fighters captured Tishrin hydroelectric dam near the town of Manbij in northern Aleppo province, which borders Raqqa.
Rebels led by the al-Qaida-linked militant group Jabhat al-Nusra captured the Furat dam on Monday, taking control over water and electricity supplies for both government-held areas and large swaths of land the opposition has captured over the past 22 months of fighting.
Rebels also stormed a second base on Tuesday.
The Observatory and the Aleppo Media Center said the rebels captured large parts of the "Brigade 80" base near the Aleppo's main civilian airport. The Observatory said there were dozens of casualties.
Rebels have been attacking Aleppo's civilian airport, which remains in regime hands, for weeks, and now appear to have removed the main defenses around the facility.
Aleppo is Syria's second largest city and the commercial capital.
While the rebels control many areas in the north and east of the country, and hold whole neighborhoods in the city of Aleppo, the government maintains a tight grip on Damascus, and several central provinces, including Homs and Hama.
For nearly a week, the rebels have been trying to slowly battle their way into the capital from neighborhoods and towns on its doorstep, and have punched to within a mile of the heart of the city.
There was more fighting in the capital on Tuesday. Activists said government warplanes struck opposition strongholds in several suburbs including Zamalka and Douma.
In Turkey, Interior Minister Muammer Guler said the death toll from an attack Monday on a border crossing with Syria's Idlib province rose to 14 from 13.
The frontier area has seen heavy fighting, although attacks on the crossings that are used by Syrian refugees and international aid agencies have been rare.
A major Syrian opposition faction accused the government of the bombing, saying it narrowly missed 13 leaders of the group including its president.
Syrian National Council President George Sabra told reporters in Turkey that the car bomb went off shortly before the SNC president and 12 other members of the group's executive council drove through a border crossing with Turkey.
"We heard an explosion nearly half an hour before we reached the border crossing point," Sabra said.
There was no claim of responsibility for the blast.
Turkey's deputy prime minister, Besir Atalay, said a preliminary investigation indicated three assailants parked a car packed with explosives in no man's land between two border gates, then detonated it remotely about 20 minutes later.
Atalay said the car had Syrian license plates. He did not say who was behind the attack, only that the probe into the blast is ongoing.
Tensions have flared between the Syrian regime and Turkey in the past months after shells fired from Syria landed on the Turkish side of the border, prompting Turkey to return fire.
Germany, the Netherlands and the United States decided to send two batteries of Patriot air defense missiles each to protect Turkey, their NATO ally.
Turkey, formerly an ally of Damascus, has backed the opposition in the uprising.