A powerful 7.8-magnitude earthquake early Monday has killed more than 500 people in Turkey and northern Syria and set off a search for survivors amid the rubble of fallen buildings.

Turkish Vice President Fuat Oktay told a news conference the death toll in Turkey had risen to at least 284 people, with more than 2,300 others injured.

Syrian health officials said at least 237 people were killed in the regions of Aleppo, Hama and Latakia.

"We hope that we will get through this disaster together as soon as possible and with the least damage," Turkish President Recep Tayyip Erdogan tweeted.

His government declared a 4th-level alarm, meaning it is asking for international help.

Turkey's Interior Minister Suleyman Soylu said there were more than 20 aftershocks. He said the earthquake affected at least 10 provinces in Turkey and that he and other Cabinet members were going to those areas.

The epicenter of the earthquake was located near Gaziantep, a key industrial and manufacturing hub close to the Turkey-Syria border. According to the U.S. Geological Survey, people reported feeling the tremors in Lebanon, Egypt and Cyprus as well.

Epicenter of a 7.8 earthquake near Gaziantep, Turkey (U.S. Geological Survey)

In the Turkish city of Mersin, resident Nurhan Kiral told VOA's Turkish service that the earthquake lasted about a minute.

"We woke up with the tremor and got out of the bed. Rubble fell from the chimney. Rubble fell from the empty space between the buildings. It was terrifying," Kiral said.

The Syrian American Medical Society said its hospitals in Syria were "overwhelmed with patients filling the hallways."

"Many hospitals are full, but some critical facilities, including Al Dana Hospital had to evacuate patients after sustaining severe damage from the earthquake," the group said in a statement. "Likewise, the Idleb Maternity Hospital was forced to transfer all newborns to a nearby hospital."

U.S. national security adviser Jake Sullivan said President Joe Biden directed the U.S. Agency for International Development and other federal partners "to assess U.S. response options to help those most affected."

"The United States is profoundly concerned by the reports of today's destructive earthquake in Turkiye and Syria. We stand ready to provide any and all needed assistance," Sullivan said in a statement.

Ukrainian President Volodymyr Zelenskyy offered his government's support as well.

"I am shocked to learn of deaths and injuries of hundreds of people as a result of the earthquake in Turkey," Zelenskyy tweeted. "We send our condolences to the families of the victims and wish the injured a speedy recovery. At this time, we stand by the friendly Turkish people and are ready to provide the necessary assistance."

European Council President Charles Michel expressed the European Union's "full solidarity."

"Deeply saddened to hear this morning about the devastating earthquake hitting parts of Türkiye and Syria," Michel tweeted. "My deepest condolences to the many families that lost lives and wishing a fast recovery of the injured."

Turkey is in one of the world's most active earthquake zones.

In 1999, 17,000 people were killed when a 7.4-magnitude earthquake - the worst to hit Turkey in decades - struck near Duzce, in the northwest of the country.

In October 2022, a magnitude-7.0 quake hit the Aegean Sea, killing 116 people and wounding more than 1,000. All but two of the victims were in Izmir, Turkey.

Some material for this article came from The Associated Press, Agence France-Presse and Reuters.