Gaza's Hamas-run health ministry said on Friday that Israeli fire killed 20 people and wounded 155 waiting to receive desperately needed aid in the besieged territory, but Israel said the reports were "erroneous".

With the United Nations warning of a looming famine in Gaza, besieged by Israel after the October 7 attack by Hamas militants, a Spanish aid ship sailed closer to the Gaza coast opening a maritime corridor from Cyprus.

Efforts to get food and other aid into Gaza have grown, including by air and sea, but fighting rages on after mediators failed to reach a truce for the Muslim holy month of Ramadan.

The health ministry in Gaza accused Israeli troops of opening fire from "tanks and helicopters" as Palestinians gathered at a roundabout in Gaza City in the north, revising upward an initial toll of 11 killed and 100 wounded.

Mohammed Ghurab, director of emergency services at a hospital in northern Gaza, told AFP there were "direct shots by the occupation forces" on people waiting for a food truck.

An AFP journalist on the scene saw several bodies and people who had been shot.

The Israeli military denied it had opened fire on the crowd.

"Press reports that Israeli forces attacked dozens of Gazans at an aid distribution point are erroneous," it said in a brief statement, adding that it was "analyzing the incident seriously".

- 'No alternative' -

The humanitarian emergency has forced some countries to use airdrops and sea routes for aid supplies because of limited land access to Gaza via Jordan, Israel and Egypt.

The Spanish aid vessel Open Arms, towing about 200 tonnes of food supplied by the US NGO World Central Kitchen (WCK), was about 30 kilometres (20 miles) off Gaza, the MarineTraffic website showed, after it left Cyprus three days earlier.

A WCK team in Gaza has built a floating jetty onto which cargo destined for people in northern Gaza can be unloaded. The group's president Erin Gore said they hoped to unload about 300,000 meals as soon as possible.

"We all know it's not enough... that's why we have to open this corridor with a continuous flow of boats," Gore said.

Cyprus has said a second, bigger vessel was being readied for the maritime aid corridor, which will be complemented by a temporary pier to be built off Gaza by US troops.

However, the air and sea missions are "no alternative" to land deliveries, 25 organisations including Amnesty International and Oxfam said in a statement.

Dire shortages have left many scrambling for scraps of aid, including Mokhles al-Masry, a displaced 27-year-old who was among many Palestinians in northern Gaza scanning the skies for signs of an aid drop.

"There is no food, nothing to feed our children. We can't even find a bottle of baby milk. We've been wandering around since early morning, hoping that a plane would drop parachutes," he said.

Amnesty's secretary-general, Agnes Callamard, said the decision to build the pier suggested that the international community seemed to accept that the war would drag on.

- Netanyahu doubles down -

Israeli Prime Minister Benjamin Netanyahu rejected international pressure and doubled down on his pledge to launch a ground assault on Rafah in the south, where most of Gaza's population of 2.4 million has sought refuge.

"I will continue to repel the pressures and we will enter Rafah... and bring complete victory to the people of Israel," Netanyahu said during a visit to a field intelligence base.

Around 1.5 million Palestinians have sought refuge along Gaza's southern border with Egypt in and around Rafah.

Israeli military spokesman Daniel Hagari said this week a "significant" number of them would need to be moved "to a humanitarian island that we will create with the international community".

- 'Qatari pressure on Hamas' -

Hamas's October 7 attack resulted in about 1,160 deaths, mostly civilians, according to an AFP tally of official figures.

Israel has carried out a relentless campaign of bombardment and ground operations in Gaza in retaliation, killing at least 31,341 people, most of them civilians, according to Gaza's health ministry.

Hamas militants also seized about 250 Israeli and foreign hostages, dozens of whom were released during a week-long truce in November. Israel believes about 130 of the captives remain in Gaza and that 32 are dead.

In a sign of mounting US exasperation with Netanyahu, US Senate leader Chuck Schumer called for a snap election in Israel, describing the veteran hawk as one of several "major obstacles" to a two-state solution and peace.

Washington and other powers have called for a reformed Palestinian Authority to take charge of all Palestinian territories after the war.

The White House welcomed Palestinian president Mahmud Abbas's appointment of Mohammed Mustafa, a long-trusted adviser on economic affairs, as prime minister three weeks after his predecessor resigned.

In Jerusalem, thousands of security force personnel were deployed on Friday before the first major prayer services since the start of Ramadan.

US, Egyptian and Qatari mediators failed to broker a new truce in time for Ramadan but Netanyahu said Thursday there was now "Qatari pressure on Hamas", who he said was "clinging to unacceptable demands".

"As of this moment, there has been no real response from Hamas," he told representatives of hostages' families.

The war has resulted in severe shortages of medical supplies across devastated Gaza, with only a fraction of hospitals partially functioning.

World Health Organization chief Tedros Adhanom Ghebreyesus said aid had been delivered to Al-Aqsa hospital in central Gaza, which he said was "struggling with water, sanitation, hygiene and waste management".