More than 100 organisations have signed a joint letter calling on Israel to stop the "weaponisation of aid" into Gaza, as "starvation deepens".

Humanitarian groups, including Oxfam and Médecins Sans Frontières (MSF), say they are increasingly being told they are "not authorised" to deliver aid, unless they comply with the stricter Israeli regulations.

Groups risk being banned if they "delegitimise" the state of Israel or do not provide detailed information about Palestinian staff, the letter says.

Israel denies there are restrictions on aid and says the rules, introduced in March, ensure that aid "reaches the population directly and not Hamas".

According to the joint letter, most major international non-governmental organisations (NGO) have been unable to deliver a single truck of lifesaving supplies since 2 March.

They say Israeli authorities "have rejected requests from dozens of non-governmental organisations to bring in lifesaving goods", citing the new rules. More than 60 requests were denied in July alone.

Aid groups' inability to deliver aid has "left hospitals without basic supplies, children, people with disabilities, and older people dying from hunger and preventable illnesses", the statement said.

Sean Carroll, CEO of American Near East Refugee Aid (Anera), said: "Anera has over $7 million worth of lifesaving supplies ready to enter Gaza – including 744 tons of rice, enough for six million meals, blocked in Ashdod just kilometers away".

Israel said that any delays in delivering aid occur "only when organisations choose not to meet the basic security requirements intended to prevent Hamas's involvement".

Cogat, the Israeli military body in charge of aid, said nearly 20 organisations that completed the registration process are bringing aid into Gaza, with roughly 300 trucks entering daily.

The UN says 600 trucks of supplies a day are needed in Gaza.

The new guidelines introduced in March update the framework for how aid groups must register to maintain their status within Israel, along with provisions that outline how their applications can be denied or registration revoked.

Registration can be rejected if Israeli authorities deem that a group denies the democratic character of Israel or "promotes delegitimisation campaigns" against the country.

"Unfortunately, many aid organisations serve as a cover for hostile and sometimes violent activity," Israel's Diaspora Minister Amichai Chikli told the Agence France-Presse news agency.

"Organisations that have no connection to hostile or violent activity and no ties to the boycott movement will be granted permission to operate," added Chikli.

Bushra Khalidi, Oxfam Policy Lead, said Israel had rejected more than $2.5m (£1.8m) of goods from entering Gaza.

She added: "This registration process signals to INGOs that their ability to operate may come at the cost of their independence and ability to speak out."