Egyptian police have launched a crackdown on street vendors selling a popular children's toy which authorities have deemed insulting to the country's president Abdel Fattah al-Sisi.

The clackers, which have become the latest toy fad in Egypt, have been dubbed "Sisi's pendulum" or more disparagingly as "Sisi's testicles".

The Giza Security Directorate said in statement on Tuesday that police had arrested 41 clacker sellers and seized 1,403 pairs of the "offensive" toy, local daily al-Masry al-Youm reported.

"The head of Directorate has decided to firmly confront the merchants of this toy and curb all negative behaviour that angers citizens," the statement said.

"A campaign has been launched over the past two days to get rid of this phenomenon and challenge the negative behaviour of children, which has had an impact on citizens' state of mind," it added.

Sources told online news website Rassd that the Ministry of Education had ordered teachers to confiscate clackers from students playing with them in state-run schools.

Sisi came to power in 2013 after leading a military takeover against the country's first freely elected president, Mohamed Morsi of the Muslim Brotherhood.

Dissidents accuse Sisi of installing a repressive regime after ousting the Morsi, when he was army chief.

Egyptian young people widely make fun of the general-turned-president on social media and have given him the disparaging nickname balaha "date" after a famous mental health patient from a 1980s film.

Egyptian authorities have proven in the past to lack a sense of humour when it comes to the president.

In December 2015, a 22 year-old Facebook user was sentenced to three years in prison after posting a photoshopped photo of Sisi with Mickey Mouse ears.

Amr Nohan, who was just five days away from finishing his compulsory military service, was charged with "attempting to overthrow the regime" in a military trial.

Nohan's imprisonment only made the photo go viral on social media, also triggering condemnations in local and international media, as well as solidarity campaigns with the young man.