In pictures: Search operations continue six days after Turkey-Syria quake

Search operations are continuing in Syria and Turkey, six days after a series of deadly devastating earthquakes hit the area - killing at least 28,000 people.

A 7.8-magnitude earthquake struck Turkey before dawn on Monday and was followed by a series of aftershocks, including a 7.5-magnitude quake.

The death toll is set to double as bodies continue to be uncovered, taking deaths to over 50,000, according to UN relief chief Martin Griffiths.

A senior UN official's visit to the only border crossing for humanitarian aid into earthquake-struck northwest Syria on Sunday has been described as "too little, too late" by the White Helmets.

"The UN's failure to act quickly to save Syrian lives in the face of a humanitarian catastrophe is utterly shameful and should be a stain on its conscience," White Helmets head Raed al-Saleh stated. 

Miraculous rescues continued in pockets of Turkey more than 100 hours after the first tremor tore apart roads and flattened hundreds of buildings while a winter storm raged over southeastern Turkey and parts of Syria.

People's survival chances fall greatly after the first 72 hours because of the cumulative effects of dehydration and cold.

It has now been over 144 hours since the first earthquake occurred.