Syrian rebels launched a coordinated assault on the main prison in the northern city of Aleppo on Wednesday in an attempt to free hundreds of regime opponents believed to be held in the facility, activists said, while an Internet blackout engulfed the country for the second time in two weeks.

The Britain-based Syrian Observatory for Human Rights said rebels detonated two car bombs simultaneously outside the walls of the central prison on Wednesday morning before trying to storm the facility. Fierce clashes are taking place between President Bashar Assad’s troops and opposition fighters around the detention centre, according to Observatory director Rami Abdul-Rahman.

There were no immediate reports of casualties.

Syrian residents and the U.S.-based Renesys Corp. said Syria’s Internet went offline on Wednesday morning at 10 a.m. local time.

“It looks like a replay of what happened on the seventh and eighth,” Renesys chief technology officer James Cowie said by telephone, referring to last week’s nationwide outage. He said the cause was not immediately clear.

“It’s entirely consistent with a technical fault at a central facility; it’s also completely consistent with a decision to use an Internet kill switch,” he said.

Preliminary data from Google Inc.’s Transparency Report website also pointed to a nationwide blackout, with Syria’s online traffic share nose-diving to zero per cent on Wednesday morning.

Syrian government websites, including the SANA State news agency, appeared to be down as well, but SANA reported on its twitter account a technical problem. It said maintenance units were working to restore the Internet as soon as possible. It did not elaborate.

An official at the Syrian communications department said an Internet cable was cut in a Damascus suburb and said it will take up to four hours to fix. The official spoke on condition of anonymity because he was not authorised to give official statements. He did not say what caused the cut.

Syrian authorities have cut phone and Internet service in select areas in the past to disrupt rebel communications when regime forces were conducting major operations.

Such widespread outages, however, have been rare. The reason for the May 7 outage is still unclear.

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