The death toll has soared past 3700 in the worst earthquake to strike Turkey this century as the World Health Organisation feared even more would die as a “perfect storm” struck.

Entire families were killed in their homes when a 7.8 quake shook Turkey and neighbouring Syria as people were sleeping on Monday (local time).

The force was so great that whole apartments crumbled in Turkish cities, leaving piles of rubble and dust where buildings once stood.

The huge quake was followed in the early afternoon by another large quake of magnitude 7.7.

The second was big enough to bring down more buildings and, like the first, was felt across the region, endangering rescuers struggling to pull casualties from the rubble.

The WHO warned rescuers were in a race against time to find survivors because of extreme weather conditions, including freezing temperatures, snow, rain and wind.

The intense cold has added to the plight of the many thousands left injured or homeless and is hampering efforts to find survivors.

Syria was already mired in a humanitarian crisis from years of war and was ravaged by a cholera outbreak and economic struggles before the latest disaster.

WHO’s regional emergency director Rick Brennan warned the region was facing a “perfect storm”.

“The convergence of all these crises is leading to enormous suffering,” he told Reuters.

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The earthquake was the biggest recorded worldwide by the US Geological survey since a tremor in the remote South Atlantic in August 2021.

It is already the highest death toll from an earthquake in Turkey since 1999, when a tremor of similar magnitude devastated the heavily populated eastern Marmara Sea region near Istanbul, killing more than 17,000.

President Tayyip Erdogan, who is preparing for a tough election in May, called it a historic disaster.

“Everyone is putting their heart and soul into efforts although the winter season, cold weather and the earthquake happening during the night makes things more difficult,” he said.

The search for victims and survivors in the village of Besnia in Syria’s rebel-held Idlib province. Photo: Getty

Syrian citizen Abdul Salam al-Mahmoud said it felt like his country was experiencing an “apocalypse”.

“It’s bitterly cold and there’s heavy rain, and people need saving,” he said.

In Diyarbakir in southeast Turkey, a woman speaking next to the wreckage of the seven-storey block where she lived said: “We were shaken like a cradle. There were nine of us at home. Two sons of mine are still in the rubble, I’m waiting for them.”

She was nursing a broken arm and had injuries to her face.

A video on Twitter, verified by the BBC, showed the moment a building collapsed in Sanliurfa, Turkey.

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Poor internet connections and damaged roads between some of the worst-hit cities in Turkey’s south, homes to millions of people, hindered efforts to assess and address the impact.

Temperatures in some areas were expected to fall to near freezing overnight, worsening conditions for people trapped under rubble or left homeless.

Rain was falling on Monday after snowstorms swept the country at the weekend.

Among the damage was Turkey’s 2000-year-old Gaziantep Castle which was built during the Roman Empire.

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The Norwegian Refugee Council said the earthquake would only add to the suffering of millions of Syrians already enduring a humanitarian crisis due to the conflict.

In the Turkish city of Diyarbakir, Reuters journalists saw dozens of rescue workers searching through a mound of debris, all that was left of a big building, and hauling off bits of wreckage as they looked for survivors.

Occasionally they raised their hands and called for quiet, listening for sounds of life.

Men carried a girl wrapped in blankets from a collapsed building in the city.

Erdogan said 45 countries had offered to help the search and rescue efforts in Turkey.