Egypt's prime minister said Thursday he does not rule out posts for the Muslim Brotherhood in his cabinet if candidates are qualified, even as police cracked down on ousted president Mohamed Morsi's Islamist group.

Hazem al-Beblawi, who was appointed on Tuesday, told AFP in a telephone interview he was still considering the makeup of his interim government after Morsi's overthrow in a popular military coup last week.

"I don't look at political association ... If someone is named from (the Brotherhood's) Freedom and Justice Party, if he is qualified for the post" he may be considered, Beblawi said.

"I'm taking two criteria for the next government. Efficiency and credibility," he added.

"So far I haven't approached anyone," Beblawi said, explaining he wanted to decide on the best candidates before asking them to join the government.

Morsi's Muslim Brotherhood has already rejected an offer from Beblawi to join the new government, and called for a mass rally on Friday against what it called "a bloody military coup".

An anti-Morsi camp meanwhile is reported to be planning a Cairo rally to mark the Muslim holy fasting month of Ramadan following weekly prayers on Friday.

The rally planned in Cairo's iconic Tahrir Square, epicentre of the 2011 uprising that toppled veteran leader Hosni Mubarak, raises the possibility of further violence following a week of bloodshed after Morsi's July 3 ouster.

In the bloodiest incident, clashes around an army building on Monday left 53 people dead, mostly Morsi partisans.

Police were searching for the Brotherhood's Supreme Guide, Mohamed Badie, after a warrant was issued for his arrest on Wednesday, in connection with the violence.

Badie and other senior Brotherhood leaders are wanted on suspicion of inciting the clashes, judicial sources said.

After a year in power through Morsi, the Brotherhood is now in tatters, with much of its leadership detained, on the run or keeping a low profile following Morsi's overthrow.

Morsi himself is currently being held in a "safe place, for his safety," foreign ministry spokesman Badr Abdelatty told reporters Wednesday, adding: "He is not charged with anything up till now," he said.

Military and judicial sources have said the ousted leader may face charges eventually.

His overthrow by the military last week, after nationwide protests demanding his resignation, has plunged Egypt into a vortex of violence.

Thousands of Morsi supporters Wednesday evening joined those camped out at the Rabaa al-Adawiya mosque in Cairo's Nasr City, to break the daily Ramadan fast.

They vowed to leave only when Morsi, the country's first freely elected president, is reinstated.

"We are gathering here for Morsi. I voted for him and I want to know where he is," said protester Mohammed, 47.

"We will stay here either until the president's return or martyrdom," he said.

The Brotherhood accuses the army of "massacring" its supporters in Monday's incident, and the army says soldiers came under attack by "terrorists" and armed protesters.

The public prosecutor pressed charges on Wednesday against 200 of the 650 people it detained during the violence.

Last week Badie gave a fiery speech in which he vowed that Brotherhood activists would throng the streets in their millions until Morsi's presidency was restored.

Mansour, appointed caretaker president by the military following Morsi's overthrow, has set a timetable for elections by early next year.

Opponents and supporters of Morsi alike have criticised the interim charter he issued on Monday to replace the Islamist-drafted constitution, which he suspended, and to steer a transition the army has itself acknowledged will be "difficult."

An official with one of the parties in the National Salvation Front (NSF), the main coalition formerly led by ElBaradei, criticised Mansour's 33-article declaration for according extensive powers to the interim president.

Many within the coalition are wary of repeating the mistakes of the last military-led transition, between Hosni Mubarak's ouster in 2011 and Morsi's election in June 2012.

The Brotherhood's demise has been applauded by three Gulf states, who quickly stepped in to help prop up Egypt's faltering economy.

Kuwait on Wednesday pledged $4 billion in cash, loans and fuel, with Saudi Arabia offering a total of $5 billion and the United Arab Emirates $3 billion.