Visitors to the website of Cairo International Airport were redirected to a different page Friday. There, hackers inserted a sign used two years ago by protesters at Rabaah al-Adawiya Square, where security forces shot and killed hundreds of people in what has been described as a deliberate and premeditated massacre. Human rights groups continue to call for an investigation into the killings, yet no officials have yet faced trial or been investigated.

The Arabic writing on the new page read, "In revenge for the blood of the martyrs killed by the military gang and [President Abdel-Fattah] el-Sisi following the coup, you will drown in the blood of the protesters you killed," as translated by Al Jazeera. "The revolution continues, and the earth does not drink blood." 

An attempt to access the URL from New York resulted in a note stating the webpage was not available.

Security forces systemically shot and killed hundreds  people -- perhaps more than 1,000 -- who were encamped outside a mosque, Rabaah al-Adawiya, in east Cairo on Aug. 14, 2013. The majority of those killed had been supporters of Mohammed Morsi, Egypt's first democratically elected president and a Muslim Brotherhood leader who was ousted by the military in July 2013. Sisi, Egypt's current president, was defense minister and head of the army at the time. 

The killings likely amounted to crimes against humanity, the organization Human Rights Watch declared in a 188-page report published one year after the massacre. It estimated that a minimum of 817 people were killed but that realistically probably at least 1,000 had died.

“This wasn’t merely a case of excessive force or poor training," Kenneth Roth, Human Rights Watch's executive director, said when the report was released. "It was a violent crackdown planned at the highest levels of the Egyptian government." Authorities have yet to carry out credible prosecutions related to the massacre, and Human Rights Watch has called for Sisi to be investigated for his role in the killings.

Now, two years after the event, Human Rights Watch called Friday for an investigation by the United Nations Human Rights Council. "Washington and Europe have gone back to business with a government that celebrates rather than investigates what may have been the worst single-day killing of protesters in modern history," Joe Stork, deputy Middle East director for the organization, said, Al Jazeera reported.

Egypt deployed additional police and bolstered security in the streets of Cairo on Friday, in anticipation of protests and demonstrations marking the two-year anniversary of the massacre, Agence France-Presse reported.