At least 500 people are believed to have died after a blast ripped through Al-Ahli Arabi Baptist Hospital in Gaza on Tuesday.
Gaza's health ministry said the airstrike was carried out by Israel while the Israeli military said the Islamic Jihad organization is responsible for the "failed shooting" that targeted Israel, Xinhua reported.
A doctor, who was present in the hospital at the time of the blast, told BBC there was total devastation at the scene of the attack - where some 4,000 displaced persons were seeking refuge.
Israel Defense Forces denied Israel's involvement in the incident and posted on X: "Following an analysis by the IDF's operational systems, a barrage of rockets was launched toward Israel, which passed in the vicinity of the hospital, when it was hit."
IDF claimed Islamic Jihad terrorist organization was behind the blast.
"According to intelligence information from a number of sources we have, Islamic Jihad terrorist organization is responsible for the failed rocket launch that hit the hospital," it said on X.
The blast occurred at a time when US President Joe Biden is expected to visit Israel.
World leaders react:
Condemning the blast, Biden wrote on X: "I am outraged and deeply saddened by the explosion at the Al Ahli Arab hospital in Gaza, and the terrible loss of life that resulted. Immediately upon hearing this news, I spoke with King Abdullah II of Jordan, and Prime Minister Netanyahu of Israel and have directed my national security team to continue gathering information about what exactly happened."
He said: "The United States stands unequivocally for the protection of civilian life during conflict and we mourn the patients, medical staff and other innocents killed or wounded in this tragedy."
French President Emmanuel Macron said striking a hospital cannot be justified.
"Nothing can justify striking a hospital. Nothing can justify targeting civilians. France condemns the attack on the Al-Ahli Arab hospital in Gaza, which made so many Palestinian victims. Our thoughts are with them. All the light must be shed on the circumstances," he wrote on X.
Canadian PM Justin Trudeau said: " I’m horrified by the loss of life at Al Ahli Arab hospital in Gaza. My thoughts are with those who lost loved ones. It is imperative that innocent civilians be protected and international law upheld. Together, we must determine what happened. There must be accountability."
World Health Organization chief Tedros Adhanom Ghebreyesus posted: " @WHO strongly condemns the attack on Al Ahli Arab Hospital in north Gaza."
He said: "Early reports indicate hundreds of deaths and injuries.We call for the immediate protection of civilians and health care, and for the evacuation orders to be reversed."
The UN Secretary-General said he was horrified by the killing of hundreds of civilians following a strike on a hospital in Gaza on Tuesday.
In a tweet, António Guterres strongly condemned the strike, adding that his heart is with the families of those who died.
The total number of fatalities in Gaza has reached at least 3,000 in the 11-day ongoing war, according to the Palestinian Health Ministry.
The death toll in Israel remains at about 1,300, with most of them killed on Oct. 7 in the Hamas surprise attacks on southern communities.