An Israel Defense Forces spokesperson said the IDF was carrying out a "high precision operation in limited areas" of the hospital.

The IDF said "senior Hamas terrorists have regrouped" inside the hospital and are using it to launch attacks.

Eyewitnesses described a state of panic inside the complex in Gaza City.

"Tanks are surrounding us. We are hiding inside the tent. We hear tank fire in the vicinity of the compound," one man said in a recorded call with his brother posted on a WhatsApp group and heard by the BBC.

Heavy gunfire could be heard around the hospital in unverified footage posted on social media.

In another voice message sent to journalists from inside the hospital Muhammad Al-Sayyid said: "The soldiers here inside the complex. There are dead and wounded, and the soldiers arrested some young men. The situation here is catastrophic."

The IDF had not publicly signalled in advance that it was planning to launch a new operation at al-Shifa.

In a video message posted in the early hours, IDF chief spokesperson Rear Adm Daniel Hagari said the Israeli military was responding to "concrete intelligence which demanded immediate action".

He said the hospital would be able to continue functioning during the raid and told patients and staff they did not have to evacuate.

Displaced people sheltering at the complex will be able to leave the hospital via an evacuation route, he said, before calling on Hamas to "surrender immediately".

A statement from the Hamas-run Gaza health ministry called the operation a "flagrant violation of international humanitarian law".

Hundreds of displaced Palestinians are sheltering at the hospital, which was raided by Israeli forces earlier in the conflict.

Al-Shifa hospital was Gaza's main medical facility prior to the conflict, but its operations have been severely disrupted after months of fighting.

Hospitals have protected status during times of war under international humanitarian law - but they can lose that protection in limited circumstances if they are being used to commit an "act harmful to the enemy".

Israel has long accused Hamas of using medical facilities as cover for its operations, which the Iranian-backed armed group denies.

The IDF said it found a network of tunnels under the hospital used by Hamas when it raided al-Shifa in November 2023, as well as weapons.

Israeli troops also carried out a major military operation on the grounds of Nasser Hospital - Gaza's second biggest medical facility - in February.

Doctors told the BBC they were detained, blindfolded and beaten during the raid, reports which prompted the UK Foreign Secretary Lord Cameron to call for "answers from the Israelis".

The IDF said it found weapons and evidence hostages had been held at the facility during its raid into Nasser Hospital.

The Israeli military launched a campaign in Gaza after Hamas gunmen killed about 1,200 people in southern Israel on 7 October and took 253 other people hostage. Gaza's health ministry says more than 31,300 people have been killed in the Palestinian territory since then.

Additional reporting by Rushdi Abualouf