Representatives of the newly-founded 'National Alliance to Support Legitimacy’ blamed recent deadly clashes in Egypt on opposition forces that have been calling for the fall of President Mohamed Morsi.

The alliance was founded on Friday by a number of Islamist groups that have been supporting Morsi, including the Freedom and Justice Party, the group from which he hails.

During a press conference held at Cairo’s Rabaa Al-Adawiya Mosque, where many thousands of Islamists have been staging a sit-in in support of Morsi, Islamist speakers stressed that their opponents are not peaceful.

"Despite statements by the callers of the 30 June protests that they will be peaceful, reality contradicts these statements as assaults were recurrent," a statement by the alliance read.

"A number of martyrs passed away because of the bullets of the thugs of [ex-president Mubarak's now dismantled] National [Democratic] Party, and those who allied with them, the National Salvation Front and the Tamarod 'Rebel' movement."

The Egyptian health ministry reported that intermittent clashes since Wednesday, largely in Nile Delta governorates, had caused seven deaths and 606 injuries.

Among the victims was a US citizen, identified as 21-year-old college student Andrew Driscoll Pochter, who died of a stab wound to the chest in Alexandria, shortly after an unidentified Egyptian citizen died from a gunshot to the head in the turmoil-hit coastal city.

"They assassinated the American journalist who documented their assaults on the Muslim Brotherhood's office in Alexandria," the alliance claimed during the conference, which was held in the attendance of thousands of Islamists participating in the pro-Morsi sit-in.

"Despite all that, the alliance stresses its goals and vision… [we will] keeping managing peaceful rallies to renounce violence and resist thuggery… We will abide by the human rights that preserve the right to defend oneself."

"We also would like to invite the political and opposition forces to take political and historical responsibility and accept calls for a national dialogue, to avoid bloodshed that will come at the hands of the corrupt National [Democratic] Party's thugs."

The alliance – which was officially announced on Friday in a press conference at Cairo's International Conference Centre – includes the centrist Wasat Party (consisting mainly of Brotherhood defectors), the Salafist Watan Party, and the Building and Development Party of the ultra-conservative Al-Gamaa Al-Islamiya group.