Internet and telephone lines were largely restored across Syria on Saturday after a two-day blackout, activists said, as fighting raged around Damascus International Airport between rebels and government forces.

"Mobile coverage and Internet are back to work in most of the Syrian cities," the Britain-based Syrian Observatory for Human Rights reported, and residents of Damascus, Aleppo and Homs confirmed that Internet, cellphones and landline phones were functioning in their areas.

After the blackout took effect Thursday, many activists and ordinary Syrians had feared the government was planning a new offensive against civilians. The government denied any role, and the cause of the blackout remained unclear.

Rebel forces continued to engage in heavy clashes with government forces in a push to take over the main commercial airport in the capital, activists said. On Saturday, the fighting was concentrated only a few miles from the airport, and Syrian jets pounded rebel positions with bombs, activists said.

"The airport is one of the most vital targets that the opposition has targeted," said Ibrahim Sharqieh, deputy director of the Brookings Doha Center. "It can have an impact on the entire situation. This is a very alarming development for the regime."

As the fighting continued, U.N. Secretary General Ban Ki-moon said the conflict in Syria had reached "appalling heights of brutality." He also warned that by early next year, the number of refugees from the conflict could reach 700,000. Human rights groups say that at least 30,000 people have been killed since the uprising began last year.