Human Rights Watch Sisi Egypt
Kenneth Roth, Executive Director of Human Rights Watch speaks during a keynote panel discussion at the International CTIA wireless industry conference in Orlando, Florida Reuters

The Executive Director of Human Rights Watch and another senior staff member have both been denied entry into Egypt for "security reasons" after being detained for 12 hours at Cairo airport.

Kenneth Roth and Executive Director of the group's Middle East and North Africa Division, Sarah Leah Whitson, had flown to Egypt ahead of the publication of a report on the mass killing of protesters by security forces last year.

The incident, known as the 'Rabaa Massacre' occured in the aftermath of the overthrow of President Mohamed Morsi, a coup which was led by current Egyptian President and previous army chief Abdel Fattah al-Sisi.

In August last year, Egyptian security forces raided two camps of protesters in the Egyptian capital, Cairo. Both were filled with supporters of Muslim Brotherhood leader Morsi and, according to the Egyptian Health Ministry, 638 people were killed in clashes - 595 civilians and 43 police officers. However, the Muslim Brotherhood claimed the death toll was higher than 2,000.

Whitson tweeted: "It's official - shortest visit to Cairo ever - 12 hours before deportation for "security reasons" - the new #egypt certainly "transitioning"."

"We are all leaving Cairo and safe. Shutting us down cannot erase what happened one yr ago and we will release report on schedule tomorrow," Human Rights Watch fellow Omar Shakir also tweeted.

Human Rights Watch are just one of many human rights groups to have criticised and condemned both Sisi and the Egyptian authorities' crackdown on dissent in the North African country.

Egyptian government officials were not immediately available for comment. They had been informed of the report's findings, which was written after a year-long investigation, but no official response had been given.