CAIRO — Egyptian prosecutors have ordered 20 people be detained for 15 more days pending an investigation, after their arrest for taking part in rare protests against a decision to hike fares on Cairo's subway system.

The Supreme State Security Prosecution said late Monday that the suspects, who were arrested Saturday, are accused of membership in an outlawed group, Egyptian parlance for the Muslim Brotherhood. They also face charges of illegal protesting.

The hikes have come as part of austerity measures meant to overhaul the country's battered economy. It was the second round of subway fare hikes since March 2017.

Although small, the protests were the first by Egyptians angered by austerity measures.

Egypt outlawed all unauthorized protests in 2013, after the military overthrew an Islamist president amid mass protests against his divisive rule.