The Syrian army launched a massive assault on rebels in Aleppo yesterday amid growing world concern about the risks of reprisals against civilians in the country’s commercial capital.

Trapped civilians crowded into basements, are seeking refuge from the bombardment

At least 29 people were killed, the Syrian Observatory for Human Rights said, contributing to a figure of at least 90 people nationwide.

The watchdog said more than 20,000 people, the majority civilians, have now died since the uprising against President Bashar al-Assad’s regime erupted in March 2011.

Troops backed by tanks and helicopter gunships, which had been massing for two days, moved on southwestern districts of Aleppo, where rebels concentrated their forces when they seized much of the northern city on July 20.

Artillery pounded Salaheddin and other neighbourhoods from 7 a.m. as ground troops advanced, an AFP correspondent reported.

Trapped civilians crowded into basements, seeking refuge from the bombardment.

“The fiercest clashes of the uprising are taking place in several neighbourhoods,” the Observatory’s Rami Abdel Rahman said.

“The regime’s forces tried to storm the headquarters of Salaheddin but, thank God, the heroes of the (rebel) Free Syrian Army repulsed the attack,” FSA Colonel Abdel Jabbar al-Oqaidi told AFP.

“We have now destroyed eight armoured vehicles,” he said. “There are 100 tanks massed on the outskirts of the district.

“The battle will be hard because there is no balance of forces but we are determined and we have faith in God.”

While the rebels’ small arms and rocket-propelled grenades are little match for the heavy armour of Assad’s forces, Abdel Rahman said “the army has not made any progress since the morning, and even lost five tanks.”

An AFP correspondent in Aleppo said rebels echoed the Observatory claim that loyalists had not advanced, but put the number of tanks lost at 10. He said rebels continued to besiege a strategic police post in the city centre, where 50 men with Kalashnikovs have been holding out for three days.

He said its capture would open a corridor between Salaheddin and the rebel-held district of Sakhur, some six kilometres to the northeast.

An activist calling himself Amer said “there are thousands of people in the streets fleeing the bombardment. They’re being terrorised by helicopter gunships flying at low altitude. There’s a large number of civilians who have taken refuge in public parks.”

Official news agency SANA reported fighting in the Furqan district where “a terrorist group was terrorising residents”.

It said two “terrorists” had been killed and three others detained, and their arms and vehicles seized.

Pro-government daily Al-Watan had warned the “mother of all battles” loomed in Aleppo as the government moved to reassert its authority after recapturing rebel-held districts of Damascus earlier in the week.

Both sides acknowledged casualties were likely to be high.

Russia warned a “tragedy” was looming but said it was unrealistic to expect the government would stand by when rebels were occupying major cities.

“We are persuading the government that they need to make some first gestures,” said Foreign Minister Sergei Lavrov, whose government has long had close ties with Damascus.

“But when the armed opposition are occupying cities like Aleppo, where yet another tragedy is brewing as I understand... it is not realistic to expect that they will accept this,” Lavrov said.

“Our Western partners... together with some of Syria’s neighbours are essentially encouraging, supporting and directing an armed struggle against the regime.”

Meanwhile, foreign ministry spokesman Alexander Lukashevich said Moscow would not cooperate with a new round of EU sanctions against Syria.

“We will not consider requests and give consent to the search of ships sailing under the Russian flag, nor to the use of other restrictive measures,” he said.

Last month, Russia attempted to ship three attack helicopters and an air defence system to Syria under a Curacao flag before being exposed by Washington.

The vessel was forced to turn back when its British insurer pulled coverage. It returned to Russia and swapped its flag for a Russian one.

Interfax news agency said Russia planned to delay shipment of the Mi-25 helicopters, which it said belong to Syria and had been taken back for upgrades, until security was restored in Syria.

Turkey, which has given refuge to defecting army officers who have formed the kernel of the FSA, warned it could “not remain an observer” as violence raged across its southern border.

“We must do what we can together in the UN Security Council, and also in the Organisation of Islamic Cooperation and the Arab League, to make sure that we can make some important progress in trying to avert this appalling situation,” said Prime Minister Recep Tayyip Erdogan.

British Prime Minister David Cameron said there were “very real concerns that we have that the Syrian regime is about to carry out some truly appalling acts around and in the city of Aleppo”.

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