BEIRUT: Syrian warplanes struck captured security buildings in Raqqa Tuesday, casting a pall over the northern city a day after euphoric rebels seized much of it and captured the provincial governor, one of the highest-ranking officials to fall into rebel hands, activists said.

Fighters also battled pockets of regime loyalists for complete control of Raqqa, a city of some 500,000 people on the Euphrates River. If the opposition succeeds, it would mark the first time an entire city has fallen into opposition hands, dealing both a strategic and a symbolic blow to President Bashar Assad's regime.

But airstrikes and intermittent clashes Tuesday raised questions about whether the rebels would be able to maintain their hold on the city.

The Britain-based Syrian Observatory for Human Rights said opposition fighters captured the governor of Raqqa province, Hassan Jalali, after clashes

overnight near the governor's office in the provincial capital with the same name. The Observatory said the head of Assad's ruling Baath party in the province, Salman al-Salman, also was in rebel custody.

Several key regime figures have defected to the rebel side, but Observatory director Rami Abdul-Rahman said Jalali is one of the highest-ranking officials to be captured.

An amateur video posted online by activists from Raqqa appeared to show Jalali and Salman seated on chairs surrounded by a group of rebels.

"We just want to get rid of the regime," one of the fighters tells the pair. The video appeared consistent with Associated Press reporting from Raqqa.

According to the state-run news agency SANA, Jalali, 62, was appointed Raqqa governor in September 2012.

An activist in the city who gave only his first name Amir said the two were detained by Jabhat al-Nusra, an al-Qaida linked group that the U.S. has designated as a terrorist organization, and other fighters who swept into the city on Monday.

"They are detained in a location secured by al-Nusra and are being treated well," he said.

The group has emerged as one of the best organized and most effective forces on the opposition side, leading successful rebel assaults on military installations around the country.

Fighting raged Tuesday near an intelligence building in the city as well as several other places, the Observatory director said, adding that "some of Raqqa is still under regime control."

The government also remained in control of military air bases outside the city and was using them to deploy warplanes to fight back against the rebel gains.

The Observatory said government warplanes carried out airstrikes on two targets in the city, causing an unspecified number of casualties. It also reported heavy fighting near an ammunition depot on the northern edge of the city. Abdul-Rahman said there were reports of more than 100 people killed over the past two days but the casualty toll could not be confirmed.

Another Raqqa-based activist, Mustafa Othman, said the warplanes struck several targets in Raqqa, including former security buildings now under the control of the rebels. He said regime elements also were holed up in two other security buildings - one in the south and the second in the north of the city.

Gunfire could be heard in the background as he spoke via Skype. He said at least six people were killed Tuesday.

He insisted Raqqa was completely liberated but said as long as the regime controls the skies "I don't know if I'll be alive in the next minute."

A Syrian government official in Damascus told the AP that the Syrian army raided "terrorist groupings" in Raqqa, causing many casualties. He spoke on condition of anonymity in line with regulations.

Rebels have been making headway in Raqqa province for weeks, capturing the country's largest dam west of the city. Anti-Assad fighters stormed Raqqa's central prison on Sunday, and swept regime forces from much of the provincial capital on Monday. That prompted cheering residents to pour into the main square and tear down a bronze statue of Assad's late father, Hafez.

The Syrian conflict started two years ago as a popular uprising against Assad's authoritarian rule, then turned into a full-blown civil war after the rebels took up arms to fight a government crackdown on dissent. The United Nations estimates that more than 70,000 people have been killed in the conflict.

The relentless violence also has devastated many cities and forced hundreds of thousands of Syrian to seek refuge abroad.

The U.N. children's agency said in a statement Tuesday that the fighting threatens the education of hundreds of thousands of Syrian children, and that 20 percent of the country's schools have been damaged in the war or are being used to shelter refugees.

"The education system in Syria is reeling from the impact of violence," said Youssouf Abdel-Jelil, the UNICEF Syria representative. "Syria once prided itself on the quality of its schools. Now it's seeing the gains it made over the years rapidly reversed."

A UNICEF assessment conducted in December determined that 2,400 schools have been damaged or destroyed and another 1,500 are being used to house displaced persons, the agency said.

Schools in Idlib, Aleppo and Daraa, where the fighting has been particularly intense, are among those most affected, the statement said, adding that more than 110 teachers and other school workers have been killed and many others aren't showing up for work anymore.

In Damascus, Syrian Deputy Foreign Minister Faisal Mekdad handed over to the Russian ambassador a man he said was a German journalist, Billy Six, who had been detained after entering the country illegally.

Mekdad did not provide any details or say how Six ended up in regime hands.

Six appears to have been working for a German conservative weekly publication, Junge Freiheit, which posted numerous articles written by Six in Syria until late November.