UN fears showdown in Aleppo is 'imminent'

United Nations human rights commissioner Navi Pilley says she fears for the people of Aleppo and that a showdown in the Syrian city appears to be imminent.

A showdown between government troops and opposition forces in Syria's largest city, Aleppo, is "imminent," the United Nations' human rights office said on Friday, as the Red Cross said it is pulling some of its foreign staff from Damascus out of concern for the safety of its workers.

The country's chaos has spread to Syria's biggest cities in some of the most widespread and sustained violence the two areas have seen in more than 17 months of conflict. Rebels have been locked in fierce fighting with government troops in Aleppo for six days and are bracing for an attack amid reports that the regime is massing reinforcements to retake the embattled city of three million people.

UN High Commissioner for Human Rights Navi Pillay said unconfirmed reports are coming out of the capital, Damascus, of extra-judicial killings and shootings of civilians during fighting in the city's suburbs. Expressing deep alarm at the situation, Pillay said the report "bodes ill for the people of that city (Aleppo)".

In a statement read aloud to reporters by her spokesman Rupert Colville, she said: "And it goes without saying, that the increasing use of heavy weapons, tanks, attack helicopters and - reportedly - even jet fighters in urban areas has already caused many civilian casualties and is putting many more at grave risk."

The statement also said there have been clashes in Homs and Deir el-Zour.

A senior UN diplomat close to the mediation effort of international envoy Kofi Annan said they are "watching the situation in Aleppo with great concern".

"The ground is shifting. We use words like 'It's fluid' - and it certainly is ... It has been a roller-coaster ride," the diplomat said. He spoke on condition of anonymity because of the delicacy of the negotiations among world powers on the UN Security Council.

The International Committee of the Red Cross said on Friday it is temporarily moving some of its foreign staff from Damascus to neighbouring Lebanon.

A Red Cross spokesman in Geneva, Hicham Hassan, said the move was prompted by security concerns but that a core team of about 50 staff would remain.

Hicham Hassan also told The Associated Press on Friday that the Syrian Arab Red Crescent was suspending some of its operations in Aleppo because of heavy fighting but the Red Cross hopes to bring its staff back into the country.

Turkey's state-run agency said a Syrian MP from Aleppo, Ikhlas Badawi, has fled to Turkey and also warned that Syria was preparing for a massive offensive on cities where rebels are fighting government forces.

The Anadolu agency said Badawi has defected in protest of the Syrian regime's "violence against the people".