Caio: An Egyptian court sentenced on Wednesday 14 Muslim Brotherhood girls to 11 years in prison each after convicting them of blocking roads, possessing bladed weapons and vandalism, according to judicial sources.

The Misdemeanor Court in the coastal city of Alexandria also ordered seven underage girls from the Islamist group be placed in state-run juvenile institutions in the same case.

The 21 girls were arrested in late October during a street protest staged by backers of the ousted Islamist president Mohammad Mursi.

The court also charged the defendants with belonging to an outlawed group and disrupting public peace.

"This ruling is flawed and represents a judicial tragedy," said the chief defence lawyer Ahmad Al Hamrawi. He added that he would appeal against it.

Hundreds of Islamists have been rounded up since July when the army deposed Mursi of the Brotherhood after enormous street protests against his year-old rule.

The military-backed authorities say the arrests have been made on orders from prosecutors mainly for alleged incitement to violence.

Osama, son of Mursi, condemned the ruling on girls, calling for "protecting the nation's honour with our blood".

"We would be bad men if we did not give up souls for our women to remain dignified," he posted on his Facebook account.

Hundreds of Brotherhood's followers, meanwhile, took to the Alexandria streets Wednesday night in protest against the ruling.

"We want to have martyrdom against the boots (the army) and police," chanted the protesters as they raised Mursi's picture. "Kill or jail me, I wait for my place in heaven."

Earlier this month, a Cairo court sentenced 12 Brotherhood students to 17 years in prison each on charges of violence and vandalism for attacking the headquarters of Al Azhar, Egypt's prestigious seat of learning. The ruling has been denounced by Islamists and rights groups as too harsh.

In September, another court banned the Brotherhood and ordered its its assets frozen. The group dismissed the ban as politically motivated.