The Supreme State Security Emergency Court on Tuesday sentenced three others to 10 years, while acquitting 14 people.
It ordered that all those convicted be placed under police probation after they serve their jail terms. The verdicts can be appealed.
Those sentenced to life include Hassan Malek, a businessman who owned stores that imported computers and electronics, and his son, Hamza.
Malek was arrested in 2015 in a police raid on his house in New Cairo. Authorities said that they found publications containing Muslim Brotherhood plans to harm the Egyptian economy, manipulate the value of the Egyptian pound against the dollar and carry out attacks on the tourism sector.
Malek, who was in court for the trial and dressed in white prison garb, denied the charges.
President Abdel Fattah el-Sisi‘s government declared the Brotherhood a “terrorist” organisation in 2014, a year after the military, then commanded by Sisi, toppled Mohamed Morsi, Egypt’s first freely elected president and a senior Brotherhood figure, following mass protests against his rule.
The authorities accuse the group of receiving funds from economic entities, businessmen and supporters to carry out violent acts against state institutions.
However, rights activists say el-Sisi has overseen a relentless clampdown on dissent in Egypt since his 2014 election. The crackdown at first targeted Islamists, including Brotherhood members, but spread to encompass political dissidents, human rights lawyers, journalists and others, says Human Rights Watch (HRW).
At least 60,000 people have been jailed on political grounds, according to an estimate from HRW.
Tuesday’s verdict came as reports emerged that US President Donald Trump‘s administration, a security ally of el-Sisi, was moving to designate the Brotherhood a foreign “terrorist” organisation, which would bring sanctions against the veteran Islamist movement.
El-Sisi has denied holding political prisoners, and his backers say the security measures have been necessary to stabilise Egypt after its 2011 popular uprising.
In a separate case, 34 people were sentenced to life in prison on Tuesday on charges including planning armed attacks in Giza and Alexandria.