TEL RIFAT, Syria — Government forces pummeled the battered city of Aleppo with airstrikes and tanks and shelled parts of Damascus and southern Syria on Monday, killing at least 100 people during a major Muslim holiday, rights groups and activists said.

The violence escalated dramatically after a one-day lull on Sunday, the start of the three-day Eid al-Fitr holiday which marks the end of the holy month of Ramadan.