Egypt is braced for more violence on Friday, with both pro- and anti-Morsi supporters planning to march through cities in several provinces after midday prayers – and the interior ministry ominously vowing to use live ammunition to defend themselves and state buildings.

Morsi supporters, centred around the ex-president's Muslim Brotherhood, are furious at the army and police-led massacre of at least 235 Islamists on Wednesday. But the army – who toppled Morsi on 3 July following days of mass protests – still rides a huge wave of nationalism, with widespread support among Egyptians who believe the Brotherhood and their allies are foreign-backed terrorists bent on destroying the country.

Egypt's government continued their defiant response to international criticism of Wednesday's massacre, with the office of the interim president – Adly Mansour, a judge seen as a frontman for Egypt's real power, army chief Abdel Fatah al-Sisi – responding defensively to Thursday's criticism from US president Barack Obama.

"Egypt appreciates the faithful positions of the world's nations, but absolutely confirms its full sovereignty," said the presidency in a statement, before underscoring that its actions were in the spirit of the 2011 revolution. Critics argue that the emergence of Egypt's new military-backed regime, and a corresponding return to favour of the country's once-hated police force, represents a return to the era of Hosni Mubarak, ousted in 2011.

Anti-Brotherhood sentiment has deepened further since Wednesday, after several reports of revenge attacks on policemen and Christians across the country – solidifying the image of Islamists as terrorists. While Morsi's fall had broadbased backing, some Morsi supporters have scapegoated Egypt's Coptic Christian community – which forms around 10% of the Egyptian population – for his overthrow.

The Brotherhood issued countered the claims on Friday, denying responsibility despite the sectarian rhetoric of many of their members. A spokesman also said that the Iman mosque in north-east Cairo, which had been filled with the rotting corpses of people who died on Wednesday, was stormed by armed security officials during the new overnight curfew.

On Thursday night, in the street outside Cairo's Zeinhom morgue, five miles away, families of victims vowed to resist the curfew, refusing to leave the street until their relatives' bodies were accepted by the mortuary. "Curse the curfew," said Atef Fatih, whose brother Mohamed was shot dead yesterday. "We don't care about it. We will wait until they let the body inside."

Morgue officials struggled to cope with the number of bodies arriving at the premises. As a result, dozens of decaying bodies lay in coffins outside, relatives piling them with ice to stop the rot. Many claimed the police had refused to record their deaths as murder.