Egypt's president has defended his government's surprise decision to hike Cairo subway fares, which sparked rare protests in which 21 people were arrested.

President Abdel-Fattah el-Sissi said in televised remarks Wednesday that the metro fare hike was needed to preserve the public service and improve quality.

Last week authorities more than tripled the standard fare from 2 to up to 7 pounds (40 cents) as part of austerity measures. It was the second round of subway fare hikes since March 2017.

In recent years the government has slashed subsidies and allowed the currency to float, causing the prices of basic goods to soar. The austerity measures have taken a heavy toll on poor and middle-class Egyptians.

A 2013 law bans all unauthorized protests.