CAIRO — Syrians poured into the streets on Friday in some of the largest antigovernment protests yet despite the shutdown of much of Syria’s Internet network, which has been crucial to demonstrators’ ability to mobilize and a major source of information for those outside the country.

The crowds protesting the authoritarian rule of President Bashar al-Assad appeared fueled in part by escalating anger about the torture and killing of a 13-year-old boy. Witnesses said protesters in dozens of communities on Friday dedicated their marches to him and other children killed during the uprising.

They defied the continuing brutal crackdown that has killed more than 1,000 people, with hundreds more rounded up in mass arrests.

On Friday, more than 30 protesters were killed in the city of Hamah, according to Rami Abdelrahman, a human rights monitor. That report could not be immediately confirmed.