What we know about the Turkey and Syria earthquake

A strong earthquake struck southeastern Turkey and neighbouring Syria in the early hours of Monday, devastating cities and killing and injuring thousands.

Here's what we know about the disaster so far:

When and where

The first 7.8 magnitude quake occurred at 04:17 am (0117 GMT) at a depth of about 18 kilometres (11 miles) near the Turkish city of Gaziantep, which is home to around two million people, the US Geological Survey said.

It was followed by a slightly smaller 7.5 magnitude tremor and dozens of aftershocks.

The quakes devastated entire sections of major cities in Turkey and war-ravaged Syria.

The region also hosts millions of people who have fled the civil war in Syria and other conflicts.

Casualties

More than 9,500 people have been killed and thousands more injured, authorities and medical sources reported, as efforts continue to save those still trapped under rubble.

Initial rescue efforts were hampered by a winter blizzard that covered major roads in ice and snow and left three major airports in the area inoperable, complicating deliveries of vital aid.

Destruction

Some of the heaviest devastations occurred near the quake's epicentre between Kahramanmaras and Gaziantep, where entire city blocks lay in ruins.

Turkey said almost 3,000 buildings had collapsed in seven different provinces, including public hospitals.

A famous mosque dating back to the 13th century partially collapsed in the province of Maltaya, where a 14-story building with 28 apartments that housed 92 people collapsed.

Social media posts showed a 2,200-year-old hilltop castle built by Roman armies in Gaziantep lying in ruins, its walls partially turned to rubble.

In Syria, the health ministry reported damage across the provinces of Aleppo, Latakia, Hama and Tartus, where Russia is leasing a naval facility.

The UN's cultural body UNESCO warned that two sites on its World Heritage List, the old city of Syria's Aleppo and the fortress in the southeastern Turkish city of Diyarbakir, had sustained damage and that several others may also have been hit.

It noted that the quake occurred in one of the longest continuously inhabited areas on the planet within the so-called Fertile Crescent, which has witnessed the emergence of different civilisations from the Hittites to the Ottomans.

Even before the tragedy, buildings in Aleppo often toppled due to poor infrastructure and many are dilapidated after more than a decade of war.

International aid

Condolences and offers of aid have poured in, including from the European Union, the United Nations, NATO, Washington, China and Russia.

Despite political tensions, both Greece and Sweden have also pledged their support for Turkey.

President Joe Biden promised his Turkish counterpart Recep Tayyip Erdogan that the United States will send "any and all" aid needed.

But US Secretary of State Antony Blinken said Tuesday that while it would work with partners to provide aid in Syria, it would not work with the government of President Bashar al-Assad, whose government is under Western sanctions over alleged humanitarian abuses during his country's nearly 12-year civil war.

The World Health Organisation said up to 23 million people could be affected by the earthquake and promised long-term assistance.