Egypt's Muslim Brotherhood has vowed to continue its resistance in defiance of the military's ouster of the country's Islamist President Mohamed Morsi.

A Brotherhood statement on Thursday also distanced the group from an assassination attempt on Wednesday against a senior army commander in the Sinai Peninsula, saying the group adheres to peaceful measures.

We will continue our peaceful resistance to the bloody military coup against constitutional legitimacy. Muslim Brotherhood statement

The statement came a day after Egypt's military-backed government tightened its crackdown on the Brotherhood, ordering the arrest of its spiritual leader in a bid to choke off the group's campaign to reinstate Morsi, now held at an undisclosed Defence Ministry facility.

"We will continue our peaceful resistance to the bloody military coup against constitutional legitimacy," the Brotherhood said.

"We trust that the peaceful and popular will of the people shall triumph over force and oppression."

The group denounced the warrants for the arrest of Mohamed Badie and nine other leading Islamists for inciting violence that left dozens dead in Cairo on Monday, saying "dictatorship is back" and insisting it will never work with the interim rulers.

On Thursday, Egypt's interim prime minister, said he did not rule out posts for the Muslim Brotherhood in his cabinet if candidates were qualified.

Hazem al-Beblawi, who was brought in by the military after Morsi's removal, told AFP news agency that he was still considering the makeup of his interim government.

"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.

The Brotherhood has already rejected the offer, and called for a mass rally on Friday.

Crackdown on Brotherhood

Its leaders are believed to be taking refuge somewhere near a continuing sit-in by the group's supporters at the Rabaah al-Adawiya Mosque in eastern Cairo.

Security agencies have already jailed five leaders of the Brotherhood, including Badie's powerful deputy, Khairat el-Shaiter, and shut down its media outlets.

The prosecutor general's office said Badie, another deputy, Mahmoud Ezzat, senior member Mohamed El-Beltagy and popular preacher Safwat Hegazy are suspected of instigating Monday's clashes with security forces outside a Republican Guard building that killed 54 people - most of them Morsi supporters - in the worst bloodshed since he was toppled.

The Islamists have accused the troops of gunning down protesters, while the military blamed armed backers of Morsi for attempting to storm a military building.

The arrest warrants highlight the armed forces' zero-tolerance policy toward the Brotherhood, which was banned under authoritarian leader Hosni Mubarak.

"This just signals that dictatorship is back," said Brotherhood spokesman Ahmed Aref. "We are returning to what is worse than Mubarak's regime, which wouldn't dare to issue an arrest warrant of the general leader of the Muslim Brotherhood."

Meanwhile, anti-Morsi protesters were reported to be planning a Cairo rally to mark the Muslim holy fasting month of Ramadan after weekly Friday prayers.

The rally planned in Cairo's 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.

Coptics targeted

The Brotherhood's refusal to work with the new interim leaders underscored the difficulties they face in trying to stabilise Egypt and bridge the deep fissures that have opened in the country during Morsi's year in office.

In a separate development, a Coptic Christian man was found decapitated on Thursday in the country's Sinai peninsula five days after he was kidnappped by unknown fifghters, security officials and witnesses told AFP news agency.

The man was found with his hands and feet bound and his head severed in the Sheikh Zuwayed area of north Sinai, they said.

A security official said "extremist groups" had captured the man on Saturday, the same day that a Coptic priest was killed.

The Sinai has been plagued by security problems since early 2011 when President Hosni Mubarak was ousted.