Egypt’s military-backed interim leadership has declared that a crackdown against two protest sites is inevitable, saying foreign diplomatic efforts to resolve its stand-off with the Muslim Brotherhood have failed.

It strongly suggested that Egypt’s sharp polarisation may spiral into even more bloodshed as thousands of supporters of ousted president Mohamed Morsi, a Brotherhood member, camp out at two main Cairo junctions and hold daily protests outside security buildings.

At stake is stability in the Arab world’s most populous country. Already more than 250 people have been killed in violence since the military ousted Mr Morsi more than a month ago, including at least 130 Brotherhood supporters in two major clashes between security forces and backers of the deposed president.

The decision agreed on by all to clear the sit-ins is final and irreversible

“The decision agreed on by all to clear the sit-ins is final and irreversible,” Prime Minister Hazem el-Beblawi said on state television, reading a statement from the Egyptian cabinet.

In response, top Muslim Brotherhood figure Mohammed el-Beltagy said the protesters are not concerned with talk of clearing the sit-ins.

“What we care about is for there to be clear talks about our position against the military coup and the importance of returning legitimacy,” he said at the main protest site in the capital’s Nasr City neighbourhood. He said the cabinet’s statement makes “clear that they lack vision with regard to the political scene.”

It was unclear what the crackdown would entail or when it would begin, but it appeared unlikely to start until next week.

The cabinet statement said the Government was keen not to take action during Ramadan, which ended yesterday.

A separate statement by the interim president described the four official days of Eid celebrations that follow the Muslim holy month as “tolerant” and “harmonious”.

Meanwhile, clashes between Morsi supporters and opponents in Alexandria left one person dead and dozens wounded. Residents of the Manshiya neighbourhood were angered by marchers who were chanting against the country’s armed forces. It was not clear what sparked the violence.