CAIRO, Nov 27 (Reuters) - An Egyptian prosecutor has ordered the arrest of two prominent activists for inciting protests, including one whose group helped lead the revolt that ousted Hosni Mubarak in 2011, a source in the prosecutor's office said on Wednesday.

The arrests of Ahmed Maher, leader of the April 6 youth movement, and activist Alaa Abdel Fattah were ordered after they took part in demonstrations outside parliament on Tuesday that defied a new law.

Twenty-four other activists were detained on Tuesday for four days pending investigation of allegations of thuggery, attacking public employees, stealing wireless devices and protesting without permission from the Interior Ministry, said the source.

The law restricting protests, passed by the army-backed government on Sunday, has angered some Egyptians and drawn fire from human rights groups who describe it as a major blow to freedom in Egypt, the most populous Arab country.

Egypt has experienced some of its worst civilian violence in decades after the army, prompted by mass protests, ousted the country's first democratically elected leader, Mohamed Mursi, on July 3. It has since introduced a political roadmap meant to lead to new elections next year.

Liberals and activists, who backed Mursi's overthrow, are now becoming more vocal against the military. (Reporting by Yasmine Saleh; Writing by Michael Georgy; Editing by Catherine Evans and Elizabeth Piper)