Syrian troops launched a broad ground assault Wednesday on rebel-held areas of the besieged city of Aleppo and activists reported clashes as opposition forces fought back in a battle that has raged for more than two weeks.

The official SANA news agency claimed regime forces have fully regained control on Salaheddine -- the main rebel stronghold in the northern city. It said the military inflicted heavy losses upon "armed terrorist groups," the government's catchall term for its opponents.

But Rami Abdul-Rahman, the director of the Britain-based Syrian Observatory for Human Rights, said troops met resistance in the offensive.

President Bashar Assad's regime has suffered a series of setbacks over the past month that point to mounting chaos in the country after a 17-month-uprising that has morphed into civil war. Four senior security officials were assassinated in Damascus, there have been a string of high-level defections including the prime minister this week, and government forces have struggled to put down rebel challenges in Damascus and Aleppo.