CAIRO — An Egyptian court on Sunday sentenced three prominent activists to three-year prison terms and heavy fines, in what was seen as the latest worrying sign of the military-backed government’s determination to suppress political dissent.

The three – Ahmed Maher, Mohammed Adel and Ahmed Douma – are best known for leading roles in the 2011 uprising that toppled autocratic President Hosni Mubarak. They were arrested for demonstrating in late November against a new law that in essence criminalizes street protests, and their sentences, the maximum penalty allowed, were the first ones levied under it.

The unexpectedly long jail terms provoked dismay among rights advocates, who have been feeling increasingly under siege at the hands of the government, despite its promises to set the country on the path to democracy. The April 6 youth movement, of which Maher was a co-founder, denounced the court proceedings.

“A three-year sentence is for criminals or drug dealers, not a political activist who was one of the driving forces behind the revolution,” the movement’s general coordinator, Amr Ali, said at a news conference.

Critics of the law restricting protests have pointed out that the current interim government owes its existence to massive nationwide rallies against Islamist President Mohamed Morsi, which paved the way for a July 3 military coup against him. However, the architect of that coup, Gen. Abdel Fattah Sisi, still enjoys enormous personal popularity.

Most Egyptians have accepted without complaint the ongoing crackdown against Morsi’s Muslim Brotherhood, and, more recently, against secular activists mounting challenges to the protest law.

Additional charges brought against the three sentenced Sunday included assaulting police officers. The men were also each fined 50,000 Egyptian pounds, equivalent to about $7,250. Under the legal system, they can appeal.

The court action comes less than a month before a scheduled nationwide referendum on Egypt’s newly rewritten constitution, a vote seen by the interim government as a crucial test of its legitimacy.

Presidential and parliamentary elections wil follow, and activists have said the protest law is aimed at stifling debate and discourse. Maher’s movement said after Sunday’s verdict that it did not believe in the government’s “road map” to democracy.