In Turkey, the death toll has risen to at least 8,574, with nearly 50,000 others reported injured, Turkish President Recep Tayyip Erdogan said in a televised briefing Wednesday, during a visit to disaster areas near the epicenter of Monday's earthquake. 

At least 2,530 people have been reported killed in Syria. 

Aid agencies and emergency workers say the death toll is likely to increase further with many people still trapped under the rubble, and freezing weather conditions hampering rescue efforts.

Countries and organizations from across the globe have responded to the crisis with money, equipment and boots on the ground. Doctors Without Borders says it has 500 staff working in Syria — some of whom lost family members in the quake. NATO said its members are sending more than 1,400 emergency response personnel, CNN reported.

Extreme winter weather is impacting rescue efforts. Aftershocks are also a potential hazard — at least 125 measuring 4.0 or greater have occurred since the 7.8 magnitude quake struck southern Turkey on Monday, according to the US Geological Survey. Though their frequency and magnitude are decreasing, 5.0 to 6.0+ aftershocks are still possible and bring a risk of additional damage to compromised structures and a continued threat to rescue teams and survivors.

Thousands of buildings collapsed in the two nations and aid agencies are warning of “catastrophic” repercussions in northwest Syria. Satellite images show the extent of the damage in the Turkish towns of Islahiye and Nurdagi near the quake's epicenter.

The World Health Organization estimates up to 23 million people could be affected by the earthquake.