Egypt's army-backed government detained the Muslim Brotherhood's leader on Tuesday after a crackdown on his supporters, underscoring its intention to crush the movement that had propelled the country's first freely elected president to power.

Egypt is enduring its bloodiest week of internal strife since the monarchy was overthrown in 1952, with about 900 people killed, including 100 police and soldiers, after the authorities broke up Brotherhood protest camps in Cairo on Aug 14.

A spokesman for a pro-Brotherhood alliance said the death toll among supporters of ousted Islamist president Mohammed Morsi, deposed by the military on July 3, was at about 1,400.

The turmoil has alarmed the United States and the European Union, but Israel and some Arab states led by Saudi Arabia have urged the West not to punish Cairo's new rulers.

Mohammed Badie, 70, the Brotherhood's leader, was taken from an apartment in Nasr City in northeast Cairo, the area where protesters demanding Morsi's reinstatement had staged a vigil for six weeks before they were violently dispersed.

He was charged in July with incitement to murder during protests before Morsi's overthrow and is due to stand trial on Aug 25 together with his two deputies.

Meanwhile, the Brotherhood appointed Mahmoud Ezzat as temporary new leader on Tuesday, the official MENA news agency reported.

Footage circulated on local media showed the bearded Brotherhood leader sitting grim-faced on a sofa in a gray robe, hands folded in his lap, while a man with a rifle stands by.

The release of the images seemed designed to humiliate the Brotherhood's most senior chief, whose arrest means the top echelon of the Islamist movement is now behind bars.

After decades as an outlawed movement, the Brotherhood emerged as the best-drilled political force after Hosni Mubarak's fall in an uprising in 2011.

Fighting terrorism

Now the state accuses it of al-Qaida-style militancy and subversion, charges the Brotherhood vehemently denies.

The whereabouts of many other senior Brotherhood politicians are unknown. Those who had been posting frequently on social media have stopped in the last two days. Arrests have extended beyond Cairo, netting provincial leaders of the movement.

The Brotherhood condemned the detention of Badie, whose 38-year-old son was killed on Friday in Cairo clashes.

"When the hand of oppression extends to arrest this important symbol, that means the military coup has used up everything in its pocket and is readying to depart," it said.

The state news agency said Badie was taken to Tora prison on the southern outskirts of Cairo, where other Brotherhood leaders are held, as well as former president Mubarak.

Morsi has been held in an undisclosed location since the army toppled him on July 3 following mass protests against him.

Tamarod, the youth organization that orchestrated the street campaign against Morsi, hailed Badie's detention.

"Arresting Badie is an important step on the path of the revolution, fighting terrorism and dismantling the terrorist group by arresting its leaders," Mohammed Abdelaziz, a Tamarod spokesman, wrote on the organization's Facebook page.

The Brotherhood, which renounced violence decades ago, has promised peaceful resistance to the army takeover.

On Monday the public prosecutor opened a new investigation against Morsi over incitement to violence. The same day, a court ruled that Mubarak, who was arrested after his overthrow in 2011, could no longer be held on a corruption charge.

Reuters-Xinhua