KAHRAMANMARAS, Turkey (AP) — Rescue workers made a final push Thursday to find survivors of the earthquake in Turkey and Syria that rendered many communities unrecognisable to their inhabitants and led the Turkish president to declare it “the disaster of the century.” The death toll topped 20,000.

The earthquake affected an area that is home to 13.5 million people in Turkey and an unknown number in Syria and stretches farther than the distance from London to Paris or Boston to Philadelphia. Even with an army of people taking part in the rescue effort, crews had to pick and choose where to help.

The scene from the air showed the scope of devastation, with entire neighbourhoods of high-rises reduced to twisted metal, pulverised concrete and exposed wires.

In Adiyaman, Associated Press journalists saw someone plead with rescuers to look through the rubble of a building where relatives were trapped. They refused, saying no one was alive there and that they had to prioritise areas with possible survivors.

A man who gave his name only as Ahmet out of fear of government retribution later asked the AP: “How can I go home and sleep? My brother is there. He may still be alive.”

The death toll from Monday’s 7.8 magnitude catastrophe rose to nearly 21,000, eclipsing the more than 18,400 who died in the 2011 earthquake off Fukushima, Japan, that triggered a tsunami and the estimated 18,000 people who died in a temblor near the Turkish capital, Istanbul, in 1999.

The new figure, which is certain to rise, included over 17,600 people in Turkey and more than 3,300 in civil war-torn Syria. Tens of thousands were also injured.

Even though experts say people could survive for a week or more, the chances of finding survivors in the freezing temperatures were dimming. As emergency crews and panicked relatives dug through the rubble — and occasionally found people alive — the focus began to shift to demolishing dangerously unstable structures.

The DHA news agency broadcast the rescue of a 10-year-old in Antakya. The agency said medics had to amputate an arm to free her and that her parents and three siblings had died. A 17-year-old girl emerged alive in Adıyaman, and a 20-year-old was found in Kahramanmaras by rescuers who shouted “God is great.”

In Nurdagi, a city of around 40,000 nestled between snowy mountains some 35 miles (56 kilometres) from the quake’s epicentre, vast swaths of the city were levelled, with scarcely a building unaffected. Even those that did not collapse were heavily damaged, making them unsafe.

Throngs of onlookers, mostly family members of people trapped inside, watched as heavy machines ripped at one building that had collapsed, its floors pancaked together with little more than a few inches in between.

Mehmet Yilmaz, 67, watched from a distance as bulldozers and other demolition equipment began to bring down what remained of the building where six of his family members had been trapped, including four children.

He estimated that about 80 people were still beneath the rubble and doubted that anyone would be found alive.

“There’s no hope. We can’t give up our hope in God, but they entered the building with listening devices and dogs, and there was nothing,” Yilmaz said.

Mehmet Nasir Dusan, 67, sat watching as the remnants of the nine-story building were brought down in billowing clouds of dust. He said he held no hope of reuniting with his five family members trapped under the debris.

Still, he said, recovering their bodies would bring some small comfort.