Heavy airstrikes by the Saudi-led coalition have hit Yemen’s capital in apparent retaliation for the killing of former president Ali Abdullah Saleh.

Sanaa’s densely populated neighbourhoods were struck by the blasts after Mr Saleh was killed by the Shiite rebels who control the city.

Residents reported heavy bombing, and a UN official said at least 25 airstrikes hit the city over the past 24 hours.

The Saudi-led coalition battling the rebels had thrown its support behind Mr Saleh just hours before his death, as the longtime strongman’s alliance with the rebels unravelled.

The UN Security Council called on all sides to de-escalate the upsurge in violence and re-engage with UN political efforts to achieve a cease-fire without preconditions.

The council called the deteriorating humanitarian situation “dire,” saying Yemen “stands at the brink of catastrophic famine”.

UN spokesman Stephane Dujarric said that despite the intensified fighting, humanitarian flights, including by the UN and the Red Cross, resumed to Sanaa on Tuesday morning.

Mr Saleh’s body, which had appeared in a video by the militias with a gaping head wound, was taken to a rebel-controlled military hospital.

A rebel leader, speaking in Sanaa, said Mr Saleh’s wounded sons had been taken to hospital, without providing further details.

The gruesome images from the previous day sent shockwaves among Mr Saleh’s followers – a grisly end recalling that of his contemporary, Libya’s Muammar Gaddafi, in 2011.

Mr Saleh’s son Salah said on Facebook on Tuesday that he will not receive condolences for his father’s death until “after avenging the blood” of the former leader.

Salah also urged his father’s followers to fight their former allies, the Shiite rebels known as Houthis.

Arab League chief Ahmed Aboul-Gheit meanwhile denounced Mr Saleh’s assassination at the hands of “criminal militias,” and warned of a further escalation of the war and Yemen’s humanitarian crisis.

Aboul-Gheit’s spokesman said the international community should label the Houthis a “terrorist” organisation.

“All means should be tackled for the Yemeni people to get rid of this black nightmare,” he said.