News agencies reported that between 15 and 30 airstrikes hit rebel-held areas of the city on Saturday, adding to a death toll of nearly 250 people from more than a week's fierce fighting between government forces and rebel fighters.

At least five people were killed early in the day in bombardments believed to have been carried out by regime warplanes, the Syrian Observatory for Human Rights said.

The strikes targeted the opposition-controlled districts of Bustan al-Qasr, al-Ansari and Kalsa, the group added.

"The regime planes focus their raids on areas where there are civilians," Mahmoud al-Shami, an activist inside Aleppo, told the German news agency DPA via a Facebook message.

"They want to kill as many civilians as they can to raise fear and force the survivors to flee the area," he added.

Local resident Abu Mohammed said: "The situation has become unbearable," as he prepared to flee the city with his wife and five children. "Everything is paralyzed."

Growing civilian death toll

For several days, violence has intensified in Aleppo, where around 250,000 people still live, aid agencies said. At least 244 civilians have been killed after being caught up in the fighting.

The dead included 43 children, according to the Britain-based Observatory, which relies on a network of activists inside Syria.

Earlier in the week, Syrian rebel groups threatened to end their participation in the February 27 ceasefire if regime attacks continued.

The International Committee of the Red Cross (ICRC) warned that the intensification of fighting threatened to create a humanitarian disaster, adding that four medical facilities on both sides of the city were hit on Friday. They included a dialysis center and a cardiac hospital.

The ICRC appealed to all parties in the conflict "for an immediate halt in the attacks," warning that there was "no safe place anymore in Aleppo."

Russia declines to act

Despite a call by Washington for Russia to pressure President Bashar al-Assad to halt its airstrikes on Aleppo, Moscow said on Saturday it would not demand the bombings stop.

Deputy Foreign Minister Gennady Gatilov told the Interfax news agency that the strikes were helping to combat jihadist groups.

The city was left out of the latest US-Russian brokered temporary truce - the second in as many months - that appeared to be holding in the regime stronghold of Latakia as well as Damascus and the nearby rebel bastion of Eastern Ghouta.

The Syrian army confirmed a "regime of calm," or lull in fighting, late on Friday, which Damascus said was designed to salvage the wider ceasefire, that was agreed in February.

A new round of UN-backed peace talks is set to start on May 10 in Geneva.

mm/tj (AFP, AP, dpa, Reuters)