The death toll from the earthquake in Turkey and Syria is likely to “more than double”, according to a United Nations emergency relief coordinator.

Martin Griffiths, speaking to Sky News on Saturday, said he expected tens of thousands more deaths.

At least 24,596 people have been confirmed dead after the 7.8 magnitude earthquake struck southern Turkey and northwestern Syria on Monday, with multiple aftershocks.

Griffiths said: “I think it is difficult to estimate precisely as we need to get under the rubble, but I’m sure it will double or more,” said Griffiths.

“That’s terrifying. This is nature striking back in a really harsh way.

“It’s deeply shocking … the idea that these mountains of rubble still hold people, some of them still alive.

“We haven’t really begun to count the number of dead.”

He said that a 72-hour period after a disaster was usually the “golden period” for rescues, which has since expired, but that survivors were still being pulled out of the rubble.

“It must be incredibly difficult to decide when to stop this rescue phase,” he said.

Griffiths said he was launching a three-month operation for Turkey and Syria to help pay for the costs of operations there.

Griffiths also told Reuters he hoped in Syria aid would go to both government and opposition-held areas, but that things with this regard were “not clear yet”.

Earlier on Saturday, Stéphane Dujarric, the spokesperson for the UN secretary-general, António Guterres, told BBC Radio 4’s Today programme that negotiations were continuing to gain access to more areas in Syria and called for “solidarity” in the relief effort.

He said: “Our message is clear, it’s time to put all politics aside. Just focus on the men, women and children who desperately need help in Syria and in southern Turkey.

“Wherever we work, we have to work with the authorities in charge. That’s just the way that UN humanitarian aid is structured. So in the rebel-held territories, we work with the authorities there; in the government-held areas, we work with the government.”

Responding to criticism of the UN’s response to the urgent need in Syria after the earthquake, he added:

“I think if I was standing in the middle of devastation and my community had been hit, I would be unhappy and I would be critical because aid never comes quickly enough. But I can tell you that the UN stands with the people of Syria, whether they live in rebel territories, whether they live in government-held territories.”

Reuters contributed to this report