Türkiye has declared a three-day national mourning period for hundreds of civilians killed in Israeli airstrikes at a hospital in the besieged Gaza Strip, joining other Muslim states like Egypt and Lebanon.

A three-day national mourning has been declared as "a requirement of our respect for thousands of martyrs, most of whom are children and innocent civilians," President Recep Tayyip Erdoğan said on X.

"As Türkiye, we feel the great suffering of our Palestinian brothers and sisters in our hearts," Erdoğan added.

Earlier, Egypt declared three days of national mourning for the victims of the Israeli airstrike on a hospital in Gaza.

"This expresses that Türkiye stands with the innocent in Palestine," ruling Justice and Development Party (AK Party) spokesperson Ömer Çelik told reporters in Ankara. "This loss, whose pain we share, is also our loss."

Denunciations poured in on Tuesday and Wednesday over the blast, which has been broadly described as a "war crime” by politicians and Human Rights Watch.

Israel, however, has denied responsibility for the air raid, blaming instead a misfiring rocket from the Palestinian resistance groups.

Footage on social media showed corpses scattered across the hospital grounds.

Thousands of Palestinians were at the hospital when the building came under bombardment, according to an Anadolu Agency (AA) reporter.

A growing chorus of nongovernmental groups and world leaders is saying the Israeli bombing campaign on Gaza – including health care facilities, residences, and houses of worship – violates international law and may constitute war crimes.

Gaza is already experiencing a dire humanitarian crisis with no electricity, while water, food, fuel and medical supplies are running out.

The conflict began on Oct. 7 when Hamas initiated Operation Al-Aqsa Flood, a multi-pronged surprise attack that included a barrage of rocket launches and infiltrations into Israel by land, sea and air. It said the incursion was in retaliation for the storming of the Al-Aqsa Mosque and growing violence by Israeli settlers.

The Israeli military then launched Operation Swords of Iron against Hamas targets in the Gaza Strip.

U.N. chief Antonio Guterres has called for an "immediate humanitarian cease-fire" to ease the "epic human suffering."

At least 3,478 Palestinians have been killed in Israeli attacks on Gaza, while the figure stands at more than 1,400 people in Israel.