WASHINGTON (AFP) - The United States expressed its concern on Tuesday after an Egyptian court sentenced Islamist former president Mohamed Morsi and 14 of his supporters to hefty jail terms.

State Department spokeswoman Marie Harf said Washington would "review the basis" for the court's decision to imprison Morsi for 20 years and was "concerned by these sentences.

"All Egyptians are entitled to equal and fair treatment before the law," she added.

Morsi was convicted of ordering the arrest and torture of demonstrators involved in clashes in 2012 when he was still Egypt's elected president.

Fourteen others were convicted of the same charges, with most also sentenced by the Cairo court to 20 years in jail.

But the court acquitted the defendants of inciting murder during the Dec 5, 2012 clashes - and thus removed the threat of the death penalty.

Egypt's first freely elected leader, Morsi came to power following the 2011 ouster of veteran strongman Hosni Mubarak in a popular uprising.

But, after just a year in power, Morsi was himself toppled by then-army chief and now president Abdel Fattah al-Sisi following more mass street protests.

Morsi's Muslim Brotherhood has been banned and targeted in a government crackdown that has seen hundreds killed and thousands thrown in jail.