CAIRO — Hundreds of Egyptian journalists objected on Sunday to a pledge by newspaper editors to refrain from publishing reports critical of the government, calling the curb on freedom of expression “a victory for terrorism.”

More than 350 journalists signed an online statement responding to the editors. It was a rare instance of public dissent since the military takeover 16 months ago and the first hint of discontent within the news media over its near-unanimous support for the government.

In a statement issued on Oct. 26, top editors from 17 state and private newspapers said they would refrain from publishing criticism of the government to support the fight against militant extremists. They rejected “attempts to doubt state institutions or insult the army or police or judiciary in a way that would reflect negatively on these institutions’ performance.”

Issued days after an unusually deadly militant attack on a military checkpoint, the editors’ statement effectively made formal de facto censorship that was already in place: Hypernationalist public sentiment and an escalating crackdown on dissent had already virtually silenced the voices of both the secular and the Islamist opposition.