Cairo: Amnesty International has criticised the Egyptian army for failing to protect anti-government protesters who reportedly came under attack in Cairo from supporters of President Hosni Mubarak.
Many protesters calling on Mubarak to resign were reported to have been injured in the clashes.
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"The army has failed in its commitment to protect peaceful protesters. The fact that such violence is allowed to continue as they stand there begs the question whether they have orders not to interfere," said Amnesty International's deputy director of the Middle East and North Africa, Hassiba Hadj-Sahraoui.
There are suspicions the army was under orders not to intervene to protect the anti-government protesters. Protests began last week against Mubarak who is seen to personify a repressive regime. He has ruled Egypt for almost 30 years.
"The Egyptian authorities cannot simply sweep the board of demonstrators. The protesters' right to peacefully demonstrate must be upheld," said Hadj-Sahraoui.
Rival groups of protesters were Wednesday reported to be fighting pitched battles in and around Cairo's Tahrir Square. Many people have been wounded and shots were heard.
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Heavy gunfire was heard near Egyptian museum in Tahrir Square and two Molotov cocktails were thrown inside the courtyard of the Egyptian museum on Wednesday evening, but the fire was put out soon afterwards, Egyptian TV reported.
Earlier, the army urged people to return home after nine days of anti-government demonstrations.
Mubarak has pledged he will not stand for re-election in September.
On Tuesday, hundreds of thousands had protested across the country against Mubarak, the culmination of more than a week of demonstrations that have left about 300 people dead according to UN estimates.
Mubarak said late Tuesday he would not run for a sixth term of office in September but he has so far refused to resign immediately.
President Barack Obama told long-time US ally Mubarak Tuesday an orderly transition of power in Egypt "must begin now" and raised doubts about the Egyptian leader's plan to stay in office six more months.
But Egypt Wednesday rejected international calls for any transfer of power. "What foreign parties are saying about 'a period of transition beginning immediately' in Egypt is rejected," foreign ministry spokesman Hossam Zaki said in a statement, charging that such calls "sought to inflame the internal situation in Egypt".
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UN secretary general Ban Ki-moon Wednesday called violence against peaceful protesters "unacceptable". Ban spoke alongside Britain's Prime Minister David Cameron in London as they called for speedy political reform.
"I am deeply concerned at the continuing violence in Egypt," said Ban. "I once again urge restraint to all the sides. An unacceptable situation is happening. Any attack against the peaceful demonstrators is unacceptable and I strongly condemn it."