One of the world’s largest and most vibrant cities fell quiet after sunset on Friday as a curfew came into force, an effort by the military-backed government to maintain order on the streets of Cairo after a day of violence that killed dozens of people. Earlier in the week, on Wednesday, almost 640 people were killed when the security forces violently dispersed two sit-ins by supporters of the deposed president, Mohamed Morsi, plunging the country into chaos.

Journalists and bloggers in the Egyptian capital said they were struck by the silence of the city, one of the world’s largest and normally loudest, which was punctuated only by the sounds of violence. Kristen Chick, a correspondent for The Christian Science Monitor, captured the somber mood in an update posted to Twitter.

The new Cairo: deserted and utterly quiet at night except for the sounds of gunfire. — Kristen Chick (@kristenchick) 16 Aug 13

The Egyptian authorities have imposed curfews several times in recent years, but residents would often venture out anyway, whether because of necessity, defiance or simply apathy. In January, tens of thousands of residents in three cities along the Suez Canal made a point of taking to the streets, some even organizing soccer games, when Mr. Morsi’s government imposed a curfew after days of violent protests.

But Friday’s curfew felt different, according to Sharif Abdel Kouddous, an Egyptian-American journalist based in Cairo, who shared his thoughts on Twitter.

Egyptians never really paid any mind to curfews. Not so now. Streets are empty. Cairo, one of the world’s biggest cities, is indoors. — Sharif Kouddous (@sharifkouddous) 16 Aug 13

— LIAM STACK