CAIRO, Jan 10 (Aswat Masriya) - Nasr City prosecution released 21 football fans from Ultras White Knights after they were arrested during a friendly match between Egypt and Tunisia on Sunday.

They were charged with "inciting riot, holding harmful signs, and destroying public properties."

Some 21 people were arrested after the Sunday match which took place at Cairo International Stadium.

The defendants remained in detention at the Nasr City prosecution for almost a day after the arrest, Ahmed Osman, lawyer at the Association of Freedom of Thought and Expressions (AFTE), told Aswat Masriya. 

The reason of the arrest was obscure. According to Osman, an altercation escalated between the defendants and security forces after changing against sons of former president Mubarak; Alaa and Gamal who were attending the match.

The Sunday match, held in Cairo international stadium, witnessed the first public appearance of both sons since the 2011 uprising.

However, an eyewitness told Aswat Masriya that the altercation happened after the defendants raised slogans against head of Zamalek sporting club, chancellor Mortada Mansour during the second half of the match.

The eyewitness also said that the defendants chanted against the police with reference to the upcoming second anniversary of "Air Defence stadium violence."

In February 2015, violence took place ahead of a football game between Zamalek and Enppi in the Air Defence stadium, leaving at least 19 people dead.