Egypt's Court of Cassation on Tuesday rejected the appeal of three activists sentenced to three years in jail for holding an unauthorised protest, according to judicial sources.

Ahmed Maher and Mohamed Adel, founding members of the April 6 Youth Movement, as well as long-time activist Ahmed Douma were convicted in December 2013 for organising illegal demonstrations, breaching the controversial protest law.

They received a three-year jail term and were ordered to pay a LE50,000 fine each.

The first level appeal court had upheld the primary court's ruling in April 2014, prompting the activists to appeal in front of the Court of Cassation, the country's highest appeal court.

Maher, Adel and Douma are accused of assaulting police officers during a demonstration outside a Cairo court, where Maher was handing himself in for questioning over his participation in another unauthorised protest.

The defence team has said that the ruling included faulty reasoning, breached the right to defence and lacked evidence of the defendants' assault on police.

The Court of Cassation's verdict is final and cannot be further appealed, according to defence lawyer Tarek El-Awadi.

"We have no solution other than to submit a petition for the case to be reconsidered, after reviewing the court's reasoning to reject the appeal," he told Ahram Online.

Over the past year and a half, thousands of Islamists and non-Islamist opponents of the regime have been arrested and tried on a variety of charges, including breaching the protest law, issued in 2013 and contested by local and international rights groups.