The earthquake that has devastated Turkey and Syria could cause economic losses exceeding $4 billion, ratings agency Fitch said.

"Economic losses are hard to estimate as the situation is evolving, but they appear likely to exceed" $2 billion and could reach $4 billion "or more", Fitch Ratings said.

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Insured losses will be much lower, possibly around $1 billion, due to low insurance coverage in the area, it added.

Nearly a week since the most devastating earthquake in recent history, rescuers in Turkey and Syria are still searching for signs of life in freezing temperatures as the death toll surpassed 33,000 and survivors expressed frustration about the rescue efforts.

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UN relief chief Martin Griffiths has said he expects the death toll to at least double after he arrived in southern Turkey on Saturday to assess the quake's damage.

The powerful earthquakes that shook Turkey and Syria this week are among the most devastating and deadliest quakes in recent history.

With the fast-rising death toll, the earthquake that hit the two countries is now among the deadliest seen worldwide in the 21st century.

On Monday, January 6, a magnitude 7.8 quake struck at 4:17 a.m. local time in the southern Turkish province of Kahramanmaras, U.S. Geological Survey said. Hours later, a 7.5 magnitude quake hit more than 60 miles away. Scores of violent aftershocks followed both quakes and continued into Tuesday.

Thousands of buildings were toppled. In addition to the climbing death toll, tens of thousands of injuries have been reported.