CAIRO (AP) — A prominent Egyptian activist imprisoned for three months has joined a growing number of prisoners in an ongoing hunger strike to protest the government’s crackdown on dissent, a Cairo-based rights group and her lawyer said Monday.

The Arabic Network for Human Rights Information said at least a dozen protesters and activists behind bars have started a hunger strike in the past week, including prominent blogger and activist Alaa Abdel-Fattah. Abdel-Fattah is awaiting a retrial after he won an appeal of his 15-year prison sentence for participating in a protest last year.

The group said Mahienour el-Masry, a secular activist sentenced for protesting as well, started a hunger strike Sunday. She was sentenced in May to two years, though her sentence was reduced to six months in July in addition to a $7,000 fine.

The group said the hunger strikes are in reaction to “unfair trials” and “noticeably prolonged detentions” without trial in cases involving freedom of expression.

Security officials say at least 20,000 people have been detained since the government crackdown began last year. Most of the detained are Islamist supporters of Egypt’s ousted President Mohammed Morsi. Late last year, the Egyptian government passed a controversial protest law that bans demonstrations without prior police approval and toughens the penalties on violators.

The government says the law is necessary to ensure stability and the rule of law after years of turmoil and amid a campaign of militant violence.

El-Masry’s lawyer, Mohammed Ramadan, said she began a hunger strike over the protest law.

“She is protesting the absence of justice and to demand that all cases based on this law be dropped. These are political cases,” Ramadan said.

Also joining the strike Sunday was a group of 11 Morsi supporters who have held without charges for months for protesting, the group said. Two other Morsi supporters have been on hunger strike for months, including U.S-Egyptian citizen Mohammed Soltan, whose health has been failing after over 200 days on strike.

Another, Ibrahim el-Yamani, has been on hunger strike for over 120 days after his one-year detention.

A Facebook page called “We are up to here!” that tracks the number of prisoners on hunger strikes posted reports filed to prosecutors showing two prisoners in the southern province of Fayoum also joined the hunger strike Sunday because of their continued detention without charges.

A protest is planned later Monday in solidarity with prisoners on hunger strike.

In June, authorities released an Al-Jazeera Arabic service journalist for health reasons after he had been on hunger strike for more than four months to protest his detention without charges.

Copyright 2014 The Associated Press.