The United Nations expressed concern about several thousand civilians who have fled Syria’s largest city Aleppo amid intensifying clashes between the government and rebel forces.

An estimated 200,000 of the city’s population have fled, the UN’s Emergency Relief Coordinator Valerie Amos said on late Sunday in New York, citing figures from the Red Cross and Red Crescent Societies.

“I call on all parties to the fighting to ensure that they do not target civilians and that they allow humanitarian organizations safe access to bring urgent and life-saving help to people caught up in the fighting," Ms. Amos said.

Government troops intensified their attacks to regain control of areas of the city held by rebels seeking to topple the regime of President Bashar al-Assad. Helicopter gunships fired on the south-eastern district of Salaheddine, according to the opposition Syrian Observatory for Human Rights.

The rebels said they had blocked the army from entering several districts in Aleppo and destroyed tanks. Their claims could not be independently verified.

At least 95 people were killed on Sunday in Syria, mainly in Aleppo and in suburban areas of Damascus and Daraa in the south, said the opposition. The opposition National Syrian Council planned talks in Cairo on Tuesday to discuss forming a transitional government, member Khaled Khuga told DPA.

Western powers have recently called on opposition groups to patch up their differences and formulate a united vision for post-al-Assad Syria.

The weekend’s clashes were the heaviest of the uprising which has claimed more than 20,000 lives since it began in March 2011, according to the Syrian Observatory for Human Rights.

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