The ruler of Dubai has said he hopes Egyptian army chief Abdel Fattah al-Sisi will not run for Egypt's presidency, days after the general indicated his willingness to stand in the election.

"I hope he stays in the army. And someone else [stands] for the presidency," Sheikh Mohammed bin Rashed al-Maktoum said in an interview with the BBC, excerpts of which were provided Monday by the channel.

Syria warned on Monday against preconditions for peace talks in Switzerland next week, a day after an opposition leader said President Bashar Assad's departure was "inevitable."

"Any person who seeks preconditions or mistakes their dreams for reality is leading to the failure of the Geneva conference before it even starts," Syrian state media quoted a foreign ministry source as saying.

A crackdown by Egypt's authorities on the Muslim Brotherhood has left hundreds of Islamic charities struggling for funds, with experts warning the move could impact this week's referendum on a new constitution.

The Tuesday-Wednesday vote has been billed as the first step in Egypt's democratic transition after the military overthrew Islamist president Mohammed Morsi in July following huge protests against his one-year rule.

More than 20 of the 200 or so Belgian Islamists who have left for Syria to fight President Bashar Assad's regime have been killed, Foreign Minister Didier Reynders said Monday.

"More than 200 people have been clearly identified or are being identified... Most have joined the most extremist groups, including the Islamic State of Iraq and the Levant (ISIL)," an al-Qaida-linked group, Reynders said in a newspaper interview.

Moscow and Washington made a joint call Monday for Syria's regime and rebels to agree to ceasefires in parts of their battle-scarred country ahead of peace talks this month.

But the two countries continued to disagree on Iran's participation in the talks, with U.S. Secretary of State John Kerry saying Tehran needs to accept plans for a transitional government if it wants to take part.

The jihadist Islamic State of Iraq and the Levant (ISIL) has taken most of the town of al-Bab in Syria's Aleppo province after fighting with rebels, an NGO said Monday.

The advance by the group in the country's turbulent north comes after 10 days of fighting pitting moderate and Islamist opposition forces against the al-Qaida inspired organisation that has killed nearly 700 people.

Foreign Minister Mohammad Javad Zarif will head to Moscow Thursday for talks with Russian President Vladimir Putin on Iran's nuclear program and on regional issues including Syria, an official said.

"Zarif will meet the Russian president as well as Foreign Minister Sergei Lavrov during his one-day trip to Moscow on Thursday," Mehdi Sanaei, Iran's ambassador to Russia, told the official IRNA news agency.

Syrian state security forces arrested on Monday a Kurdish journalist working for an Iraqi news outlet in the northern city of Qamishli, a relative told Agence France Presse.

Pishwa Bahlavi was filming a report about events in the city marking the Prophet Mohammed's birthday for Rudaw, an Iraqi Kurdish media company, when he was detained, said his cousin Dilkhaz Bahlavi.

Iraqi leaders should address the underlying causes of a protracted surge in violence plaguing the country, U.N. Secretary General Ban Ki-moon said on Monday during a visit to Baghdad.

"I would urge the leaders of the country ... to address the root causes of the problems," Ban said.

Syrian Foreign Minister Walid Muallem will visit Russia ahead of the Geneva 2 peace talks on the crisis due to begin in Switzerland later this month, Damascus's ambassador to Moscow said Monday.

"He will be in Moscow prior to Geneva 2," Riyad Haddad told the Interfax news agency, without specifying the date.