CAIRO, Aug 12: Egypt's judiciary extended ousted president Mohamed Morsi's detention on Monday as his supporters marched through Cairo in defiance of the expiry of a government ultimatum to dismantle their huge protest camps.

The judiciary said it was extending Morsi's detention for a further 15 days pending an investigation into his collaboration with the Palestinian Islamist group Hamas which rules Gaza.

Overthrown by the military on July 3, Morsi was placed in detention on July 26 over his links with the militant group.

He is to be questioned on whether he collaborated with Hamas in attacks on police stations and prison breaks in early 2011, when Islamist and other political inmates escaped during a revolution which overthrew strongman Hosni Mubarak.

The court said on June 23 that Hamas

militants facilitated the escape of prisoners. At the time, Morsi, then a senior Muslim Brotherhood leader and whose whereabouts are now being kept secret, told a television station that local Egyptians had helped the prisoners escape.

On the streets of Cairo, hundreds of demonstrators waving Egyptian flags and carrying pictures of the deposed leader marched through the central neighbourhood of Ramses, as tensions rose over a threatened crackdown by the authorities.

Morsi loyalists, led by his Muslim Brotherhood movement, have kept in place two sit-ins in the capital and have also staged almost daily demonstrations around Egypt against his ouster.

The country's army-installed interim leaders have repeatedly warned them to leave, offering the Brotherhood a return to political life in exchange for an end to the protests.

With over 250 people killed in clashes since Morsi was overthrown and detained, authorities say they are eager to avoid more bloodshed.

“There will be a series of gradual steps. We will announce every step along the way,” an interior ministry general said.

Once the siege begins, the protesters will be “surrounded”, no one will be let into the sit-ins and the protesters will be given several

warnings to leave, another security official said. “This will last two to three days.”

At the main Rabaa al-Adawiya sit-in, dozens of men wearing helmets and holding clubs on Monday guarded makeshift brickwall barriers.

Some in the camp acknowledged that police will eventually break through. “We will have martyrs. It will be a high price to pay, but there will be victory in the long run,” one said.

Al-Azhar has announced a last-ditch effort to resolve the tense political standoff and called for reconciliation talks between the rivals.

But the Muslim Brotherhood is unlikely to join talks sponored by Al-Azhar as its grand imam, Ahmed al-Tayyeb, sat alongside General Abdel Fattah al-Sisi when the army chief announced Morsi's overthrow.

Morsi loyalists have called for new protests on Tuesday after again rallying to demand his reinstatement and condemn the army.

Senior Muslim Brotherhood official, Farid Ismail, told a news conference:

“We want to send a message to the coup leaders: the Egyptian people insists on continuing its revolution ... And the people will insist on turning out in all squares.” The interim leadership has drawn up a political roadmap for Egypt's transition which provides for new elections in 2014.

Morsi's turbulent single year in power polarised Egyptians and his ouster has deepened divisions.

His critics say he concentrated power in Brotherhood hands and that under his tenure political divisions spilled out onto the streets in deadly clashes while the economy tumbled.

On June 30, millions took to the streets to demand Morsi's ouster, openly calling on the army to remove him.

The interim leadership is under heavy pressure at home to crack down on the pro-Morsi protests, and it has been pressed by the international community to avoid bloodshed.

“I think (authorities) will go very tenderly,” said H.A. Hellyer, a non-resident fellow at the Brookings Institute. “Their concern isn't domestic because public opinion is strongly in favour of breaking up the protest.

International condemnation is what they're afraid about.” Senior US, EU and Arab envoys have flown into Cairo to try to persuade the two sides to find a peaceful way out of the crisis, but they have all left empty-handed. —AFP