Egyptian security officials say police have arrested 21 people for protesting against the government's surprise decision to hike fares on Cairo's subway as part of austerity measures meant to overhaul the economy.

They say Saturday's arrests were mostly at Helwan metro station on the southern outskirts of Cairo.

Videos circulating online show dozens of outraged commuters yelling and chanting anti-government slogans at Cairo metro stations, with some jumping over electronic ticket gates to avoid paying fares.

The officials spoke on condition of anonymity because they were not authorized to brief the media.

The hike, the second since March 2017, was by up to 250 percent, raising fares from two to up to seven Egyptian pounds (11 U.S. cents to 39 cents) depending on the number of stations commuters travel.