"Famine is unfolding before our eyes. Urgent action is needed now to halt and reverse starvation," the foreign ministers of 24 countries said in a joint statement.
"We call on the government of Israel to provide authorisation for all international NGO (non-governmental organisations) aid shipments and to unblock essential humanitarian actors from operating," the statement said.
"All crossings and routes must be used to allow a flood of aid into Gaza, including food, nutrition supplies, shelter, fuel, clean water, medicine and medical equipment."
Israel has denied responsibility for hunger spreading in the Gaza Strip, accusing Hamas militants of stealing aid shipments - which Hamas denies.
However, in response to a rising international uproar, Israel late last month announced steps to let more aid into the enclave, including pausing fighting for part of the day in some areas and announcing protected routes for aid convoys.
Some governments, however, say much more aid is needed.
The statement was signed by the foreign ministers of Australia, Belgium, Canada, Cyprus, Denmark, Estonia, Finland, France, Greece, Iceland, Ireland, Japan, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and the UK.
The European Union later on Tuesday sent an updated statement to include EU members Italy and Latvia as signatories of the statement.
The EU's foreign policy chief Kaja Kallas, and two other members of the European Commission also signed the statement.
Some EU member countries, including Germany and Hungary, did not sign it.
Israeli planes and tanks bombarded eastern areas of Gaza City, killing at least 11 people, witnesses and medics said on Tuesday, with Hamas leader Khalil Al-Hayya due in Cairo for talks to revive a US-backed ceasefire plan.
The latest round of indirect talks in Qatar ended in deadlock in late July with Israel and Palestinian militant group Hamas trading blame over the lack of progress on a US proposal for a 60-day truce and hostage release deal.
Israel has since said it will launch a new offensive and seize control of Gaza City, which it captured shortly after the war's outbreak in October 2023 before pulling out.
Israeli Prime Minister Benjamin Netanyahu's plan to expand military control over the Gaza Strip, expected to be launched in October, has increased a global outcry over the widespread devastation, displacement and hunger afflicting the enclave's 2.2 million people.
It has also stirred criticism in Israel, with the military chief of staff warning it could endanger surviving hostages and prove a death trap for Israeli soldiers.
It has also raised fears of further displacement and hardship among the estimated one million Palestinians in the Gaza City region.
