The lawyer and family of one of Egypt's most prominent pro-democracy activists, Alaa Abdel-Fattah, say he has been released from prison after serving a five-year sentence for taking part in protests.

His sisters, Mona and Sanaa Seif, posted on Facebook on Friday that "Alaa is out," along with a video of him at home, playing with a dog.

His lawyer, Khaled Ali, confirmed the release by posting: "Thanks God, Alaa Abdel-Fattah at home."

Abdel-Fattah was sentenced to five years for taking part in a peaceful demonstration in 2013 after the military's ouster of Egypt's freely elected but controversial Islamist President Mohammed Morsi.

His imprisonment was part of a wider crackdown on the pro-democracy movement that began with the 2011 uprising that toppled long-time President Hosni Mubarak.