The war launched by the United States and Israel against Iran has spread across the Mideast and beyond, with Lebanon's Hezbollah entering the fray and a British military base in European Union member Cyprus coming under attack.

"Widening hostilities across the Middle East are putting civilian lives in grave danger," said Mirjana Spoljaric, president of the International Committee of the Red Cross.

"The scale of major military operations flaring across the Middle East risks embroiling the region -- and beyond -- into another large-scale armed conflict that will overwhelm any humanitarian response."

The Geneva-based ICRC acts as the guardians of international humanitarian law, the set of rules which seeks to limit the effects of armed conflict. The rules protect people who are not or are no longer participating in hostilities and restricts the means and methods of warfare.

"All parties to armed conflict have an obligation to uphold the rules of war, which are unequivocal," said Spoljaric.

"Civilians and civilian infrastructure must be spared from hostilities. Schools must remain sanctuaries for learning where children can feel safe and protected from attacks, and hospitals must remain sanctuaries for saving lives."

The ICRC chief said medical personnel and first responders, including Red Cross and Red Crescent national societies, had to be protected and allowed to carry out their work safely.

In a letter to Spoljaric, Iran's ambassador in Geneva, Ali Bahreini, said the US and Israeli attacks had seriously violated international humanitarian law.

"The deliberate and indiscriminate targeting of civilians and civilian objects -- including hospitals, medical facilities and schools -- constitutes a grave breach of the fundamental principles of distinction and proportionality", he said, as well as protections afforded under the Geneva Conventions, which form the core of international humanitarian law.

Bahreini urged the ICRC chief to condemn the strikes.

Iran "reaffirms its commitment to the international humanitarian law and expects full respect for the Geneva Conventions", he said.