Human Rights Watch and the European Union have voiced concerns over Egypt's latest arrests of prominent activists and have called for their release.

Thursday's statement by the New York-based watchdog says the arrests show that "the state of oppression in Egypt has sunk so low" under President Abdel-Fattah el-Sissi.

Earlier, the EU said the increasing arrests are a "worrying development."

Egypt rejected the EU statement, saying it's "a mistaken reading of the situation in Egypt."

Authorities have arrested several critics, including a well-known blogger and a socialist activist, after el-Sissi's re-election in a March vote in which he faced no serious challengers.

The arrests are part of a wider crackdown on dissent since the 2013 military ouster of an elected Islamist president following mass protests against his one-year divisive rule.