Egypt's High State Security Prosecution on Monday handed 15-day detention orders to 20 people pending investigations into their alleged participation in protests at various Cairo metro stations against Friday's increase in ticket prices.

The prosecution charged the defendants with illegal assembly that endangers security and public order, as well as with resisting authorities.

Defendants were also charged with committing crimes with the aid of an outlawed group which aims to obstruct state institutions from carrying out their duties -- a presumable reference to the now-banned Muslim Brotherhood.

Egypt raised ticket prices for the Cairo metro on Friday.

A number of small protests by commuters against the decision arose at various metro stations.

Protests have been rare in Egypt since the country passed a law in 2013 criminalizing demonstrations without official approval from the interior ministry. Violators face up to five years in prison.

Commuters' confusion and objections came after the transport ministry hiked metro fares from a flat rate of EGP 2 per ride to between EGP 3 – 7 based on a new zone system. It is the second fare hike since March 2017.

Rides up to eight stops will now cost EGP 3, whereas rides from nine to 15 stops will cost EGP 5. Rides 16 stops and over will cost EGP 7, which constitutes a 250% increase over the previous flat rate.

The Egyptian Transport Ministry has defended its decision, arguing that the raise comes at an appropriate time and is necessary in order to overcome the vital service's significant fiscal deficit.

Transport Minister Hisham Arafat told DMC TV's night time programme last week that the increase is needed to finance and upgrade the infrastructure of the first metro line, which is now 30 years old and in dire need of EGP 30 billion in renovations.