Israel is watching "with great concern" the developments in Egypt where Islamist President Mohammed Morsi ousted his powerful defence minister and army chief following a deadly attack in Sinai.

In a surprise move aimed at curbing the Egyptian army's sweeping powers, Morsi on Sunday forced retirement upon both Field Marshal Hussein Tantawi and the army's Chief of Staff Sami Anan.

China said Monday that a top aide to Syrian President Bashar Assad will visit this week for talks with Chinese leaders, as violence rages in the country.

Bouthaina Shaaban, a "special adviser" to the Syrian president, will visit from Tuesday for talks with Chinese Foreign Minister Yang Jiechi and other officials, the foreign ministry said in a statement.

Horrific videos purportedly showing Syrian rebels throwing the bodies of postal workers off a roof and a man's throat being savagely cut have appeared online, raising fresh concerns about atrocities in the increasingly brutal conflict.

Three videos all showing apparent events in the province of Aleppo, including a bound man being repeatedly shot, were posted on YouTube on Monday but their authenticity could not immediately be verified.

Al-Qaida's front group in Iraq has claimed 28 attacks between mid-June and the end of July, including a coordinated assault on an anti-terror department in central Baghdad two weeks ago.

The Islamic State of Iraq (ISI) said it killed 70 people in the July 31 attack, but Iraqi security and medical officials put the total death toll for violence in Baghdad that day, including the attack on the anti-terrorism directorate, at 21.

Egypt's Islamist President Mohammed Morsi has denied trying to marginalize the army after he ordered the retirement of his powerful defense minister, saying he was acting in the interests of the country.

However, the Egyptian press on Monday described Morsi's move as "revolutionary", with some saying it was aimed at ending the power of the Supreme Council of the Armed Forces (SCAF).

Syrian forces bombarded rebel strongholds around Damascus Monday and rounded up residents in a massive raid in the heart of the capital as fighting raged in the second city of Aleppo, activists said.

Security forces raided houses and shops in the center of Damascus in the biggest operation of its kind in the city since the launch of the uprising against President Bashar Assad's regime in March last year, they said.

Iranian President Mahmoud Ahmadinejad arrived on Monday in Saudi Arabia ahead of an extraordinary summit in Mecca expected to focus on the Syria conflict, on which Tehran and Riyadh have taken opposing sides.

Ahmadinejad arrived in the Muslim holy city of Medina, in western Saudi Arabia, SPA state news agency said, adding that he visited the mosque and tomb of Islam's Prophet Mohammed.

French military medics started on Sunday to set up a field hospital at Jordan's main camp for Syrian refugees, as residents expressed fear that their stay could turn into a long one.

Refugees gathered to watch 85 French medical officers assemble the hospital of 30 large khaki tents as well as 80 tons of medical equipment and aid supplies at the desert camp outside the city of Mafraq in northern Jordan.

The Syrian army pressed its assault on rebels in commercial capital Aleppo on Sunday, as both sides reported atrocities.

The exiled opposition said pro-government militia had executed 10 civilians in a roundup in the flashpoint central city of Homs, while the official SANA news agency reported the murder of one of its staff, in the latest case of a pro-government journalist being killed.

Egypt's Islamist President Mohammed Morsi on Sunday ordered the surprise retirement of his powerful defense minister and scrapped a constitutional document which handed sweeping powers to the military.

Field Marshal Hussein Tantawi, who ruled Egypt for more than a year after the revolution that toppled former president Hosni Mubarak, was replaced by Abdel Fattah al-Sissi.