UNITED NATIONS - The UN Security Council called Tuesday on all sides in war-torn Yemen to “de-escalate” and return to talks as the conflict there took an ominous turn with the killing of ex-president Ali Abdullah Saleh.

“The members of the Security Council call all sides to de-escalate and to recommit and re-engage without preconditions in the UN-led political process to achieve a durable ceasefire,” Japanese ambassador Koro Bessho, the council’s president, said after a closed-door meeting on the situation. The UN on Tuesday called for a “humanitarian” truce in air strikes and fighting in Yemen as it seeks to deliver aid to people trapped in the capital Sanaa.

As the UNSC prepared to discuss Yemen on Tuesday, several international aid agencies chimed in to condemn a surge in violence in the war-torn country, and demanded unimpeded access to civilians.

“I... sent a message asking for a truce, a peace pause, a humanitarian pause, for the parties to stop shooting, stop fighting, stop air strikes, so the people can go to hospitals, can go to seek safety ... and go to also find a place for water and food,” UN humanitarian coordinator Jamie McGoldrick told reporters in Geneva by phone from Sanaa. “Our ability to get to people over the last five days has been impeded because of the air strikes, because of the fighting, and our life-saving support activities were blocked,” he said.

Meanwhile, Yemen’s Huthi rebels moved to cement their grip on the capital Tuesday after killing former president Ali Abdullah Saleh as he fled the city following the collapse of their uneasy alliance.

Residents reported a few minor clashes between the Huthis and Saleh supporters late on Monday in southern districts which had been loyal to the slain strongman.

But there was no repetition of the heavy fighting that had rocked Sanaa for the five previous nights.

A least 234 people were killed and 400 wounded in those clashes, the International Committee of the Red Cross said on Tuesday.

New checkpoints manned by rebels sprung up across Sanaa as their leaders hailed their control of the capital.

“We declare the end of security operations and the stabilisation of the situation,” senior Huthi official Saleh al-Sammad told the rebels’ Almasirah television channel late on Monday.

Sammad said he had ordered the security forces to “take steps against the saboteurs and all those who collaborated with them”.

The capital was awash with unconfirmed rumours of widespread arrests of suspected Saleh supporters in the army and the rebel government.

The former strongman retained the loyalty of some of the best equipped units of the army after he was forced to step down as president in 2012.

Saleh, who ruled Yemen for three decades, had joined forces with the Huthis in 2014 when they took control of large parts of the country, including the capital.

But that alliance unravelled over the past week as the former leader reached out to the Saudi-led coalition that has waged an air campaign against the Huthis since March 2015.

In a sign of confidence, the Huthis called a mass rally for Tuesday afternoon to celebrate their “foiling of the plot” hatched by Saleh to change sides in Yemen’s devastating civil war.

The Saudi-led coalition stepped up its bombardment of the capital on Monday night, carrying out at least seven strikes on the rebel-held presidential palace, witnesses said.

There was no immediate word of any casualties.

Yemen’s war has left thousands dead, led to one of the world’s worst humanitarian crises and deepened tensions between Middle East rivals Saudi Arabia and Iran.

Iranian President Hassan Rouhani warned on Tuesday that those attacking Yemen would regret it.

“The people of Yemen will make their aggressors regret their actions,” he said in a televised speech.

The commander of Iran’s elite Revolutionary Guards, Mohammad Ali Jafari, said Saleh was killed because he had been trying to overthrow the Huthis.

“The traitor Saudis are seeking to create insecurity in the region under orders from the United States and working alongside Israel... We witnessed their attempt to launch a coup against (the Huthis), which was strangled at birth,” Jafari said.

Arab League chief Ahmed Abul Gheit condemned Saleh’s killing, saying that the “way it was done reveals to everyone the criminal nature” of the Huthis.

Saleh was forced to step down in 2012, after his forces waged a bloody crackdown on peaceful Arab Spring-inspired protests calling for his ouster.

The 75-year-old had survived civil war, rebellion in the north, an Al-Qaeda insurgency in the south and a June 2011 bomb attack on his palace that wounded him badly.

The Huthis announced his death on Almasirah, and a video provided to AFP by the rebels showed what appeared to be a dead Saleh with a severe head injury, his body wrapped in a floral-print blanket.

A military source said the Huthis had stopped their four-car convoy about 40 kilometres (25 miles) south of Sanaa and shot dead Saleh and two other officials.

In a televised speech on Monday, rebel chief Abdul Malik al-Huthi made no mention of Saleh’s death but expressed his satisfaction at the day’s events.

“Today marked the failure of the conspiracy and treason, a black day for the forces of aggression,” he said.