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The European Union's top diplomat was heading for Cairo Wednesday, a day after an interim government was sworn in to replace Islamist president Mohamed Morsi, toppled by the military two weeks ago.

Announcing the surprise visit, the office of EU foreign policy chief Catherine Ashton said her visit was to press the case for a swift return to democratic rule.

"I am going to Egypt to reinforce our message that there must be a fully inclusive political process, taking in all groups which support democracy," Ashton said.

Both the Muslim Brotherhood, the influential movement from which Morsi hails, and the ultra-conservative Al-Nur party refused to take part in the new administration.

Brotherhood spokesman Gehad El-Haddad immediately rejected the 35-member cabinet that was sworn in on Tuesday.

"We don't recognise its legitimacy or its authority," he told AFP.

The government is headed by liberal economist Hazem al-Beblawi.

Army chief Abdel Fattah al-Sisi, the general behind the popularly backed coup that overthrew Morsi, becomes first deputy prime minister and minister of defence.

Tuesday's swearing-in ceremony took place just hours after deadly clashes between the security forces and Morsi's supporters in Cairo and nearby Giza.

Officials said seven people were killed and 261 wounded in the clashes. Hundreds of protesters were also arrested.

On Monday, US envoy Bill Burns -- the most senior American official to visit since the July 3 coup -- had appealed for an end to the violence rocking the Arab world's most populous nation.

Within hours however, thousands of Morsi supporters were on the streets of the capital protesting at the president's overthrow and his detention by the military.

Hundreds of them battled the security forces and two people died in clashes around the central Ramses area near Tahrir Square, while another five were killed in Giza, emergency services told AFP.

A security source cited by state media said 401 protesters were arrested in the Ramses area alone, and at least 17 security personnel were injured.

This was the first major violence in the capital since dozens of Morsi supporters were shot dead outside an elite army barracks early last week.

The United States condemned the violence. State Department spokesman Patrick Ventrell said it made the transition "much more difficult," but he insisted Washington was not taking sides.

Washington has refrained from saying Morsi was the victim of a coup, which would legally require a freeze on some $1.5 billion in US military and economic assistance to Cairo.

These latest deaths bring to more than 100 the number of people killed in the unrest since the coup, according to an AFP tally.

The caretaker government unveiled on Tuesday included three women ministers and three Coptic Christians.

Analyst Samer Shehata said Egypt's budget deficit, reforming the interior ministry, establishing the rule of law and restoring security in the Sinai peninsula were among the pressing issues for the new government.

"How to deal with the protesters on the street at the moment is another very serious issue," he added.

Standard & Poor's ratings agency said Tuesday it would keep its credit rating for Egypt unchanged after Gulf states pledged billions to support the post-coup government.

Ten weeks after cutting Cairo's sovereign rating to junk-level CCC+, S&P said it would hold the rating there, with a "stable" outlook, despite the July 3 military coup.

During his single year of turbulent rule, Morsi was accused of concentrating power in Brotherhood hands, sending the economy into freefall and failing to protect minorities.

But the Islamist leader's supporters say his overthrow was an affront to democracy.

Egypt's new rulers voiced "strong resentment" on Tuesday at comments by Turkey's Islamist Prime Minister Recep Tayyip Erdogan backing Morsi as the country's only legitimate president.

The diplomatic spat came as the authorities tightened the screws on Morsi's backers, freezing the assets of 14 top Islamists, including nine Brotherhood leaders.