Syrian forces and rebels waged fierce battles in several regions on Saturday, a day after President Bashar al-Assad said in an Egyptian publication that opposition fighters would not be victorious in their fight against his government.

The government and opposition activists say fresh clashes erupted in the Aleppo region, on Saturday, where Mr. Assad's forces have been trying to dislodge rebel strongholds. The state-run SANA news agency says 20 “terrorists” were killed as government forces removed militants from “hideouts.”

The opposition Syrian Observatory for Human Rights says government shelling and raids are under way in Aleppo and other regions, including Homs and Dara'a.

On Friday, the Al-Ahram Al-Araby weekly published an interview with Mr. Assad in which he said the armed groups exercising terrorism against the state were not popular within society. He also said the “door of dialogue” remained open.

U.N. Secretary-General Ban Ki-moon has said the government and the opposition in Syria appear determined to resolve the crisis militarily. Mr. Ban said Syria will be a top issue as he meets with world leaders at the U.N. General Assembly. The sessions begin on Tuesday.