For a westerner, Tiananmen Square instantly conjures up the horror of a tyrannous dictatorship turning its military might against its own people; of the lone man, shopping bags in his hands, standing defiantly against the approaching People’s Liberation Army tanks. I doubt many of us have even heard of the Rabaa al-Aadawiya Square in Cairo, where more than 1,000 protestors were massacred by Egypt’s military and police last August. This “indiscriminate and deliberate use of lethal force”, according to Human Rights Watch, represents “one of the world’s largest killings of demonstrators in a single day in recent history”, and probably exceeds the horror of Tiananmen.

The Human Rights Watch report is a frightening indictment of the regime that overthrew the Muslim Brotherhood president, Mohamed Morsi, last July. There were at least five separate incidents of “mass protestor killings” in the two months that followed – “many of Egypt’s public squares and streets were awash with blood.” As well as violating international human rights law, Human Rights Watch judged that these massacres “likely amounted to crimes against humanity” on the grounds of their “widespread and systematic nature”, as well as evidence suggesting these killings “were part of a policy to attack unarmed persons on political grounds”.

This was no heavy-handed response to an aggressive demonstration, but a planned campaign of terror against opponents of the new regime. In a sign that Cairo will not tolerate any scrutiny of its bloody clampdown on dissent, Egypt’s government has responded by claiming that Human Rights Watch’s investigation was illegal and that its activities “constitute a flagrant violation of state sovereignty under international law”. Its plea is to be left to kill without any embarrassment.

The bloodshed in Gaza has understandably exercised western public opinion, not least because of the role of western governments in arming and backing Israel’s administration. But the west is no less complicit in the atrocities committed by Egypt’s regime, now fronted by president Abdel Fatah al-Sisi. Egypt receives $1.5bn (almost £900m) of military aid a year from the US, and in June the Obama administration released $575m of aid that had been frozen in the aftermath of the coup. Britain resumed its sale of arms to Egypt in November.

One of al-Sisi’s advisers is none other than Tony Blair, a man whose repeated work for dictators – such as Kazakhstan’s human rights-abusing regime – should surely leave him with the permanent title of “Britain’s disgraced former prime minister”. As Human Rights Watch’s executive director, Kenneth Roth, put it – after he was deported from Egypt earlier this week: “The message sent so far is that Egypt can get away with mass murder.”

Too little has been said about Egypt’s human rights crisis. More than 40,000 people were detained or indicted in the first 10 months after the coup and, according to Amnesty International, the regime is using methods of torture from “the darkest days of the Hosni Mubarak era”. With “rampant torture, arbitrary arrests and detentions”, there has been a “catastrophic decline in human rights”. There have been claims of rape against male political dissidents; the use of electrocution, including on prisoners’ testicles; and in one case, a hot steel rod was inserted in the anus of a dissident who later died.

It is not just members of the Muslim Brotherhood – now banned as a terrorist organisation – who have been repressed. Three prominent leaders of the initial revolution that overthrew Mubarak’s regime in 2011 have been locked up for three years. Leftwing activists, such as Alaa Abd El Fattah, have been put on trial for “unauthorised protests”. Despite al-Sisi’s attempts to buttress his regime with democratic legitimacy, just 47.5% of Egyptians voted in the June election.

Egypt is in the grip of a violent tyranny that brooks little dissent. And just as the west is complicit in Israel’s attack on Gaza, it equally shares some responsibility for the actions of Egypt’s regime. The question is surely, how many more corpses until we start holding those responsible to account?