A ship carrying 200 tonnes of aid for Gaza left Cyprus in a pilot project to open a sea corridor to deliver supplies to a population that aid agencies say is on the brink of famine.
While welcoming the project, however, senior UN officials said it could not replace the delivery of humanitarian aid by land from Egypt and Jordan.
Separately, the World Food Programme (WFP) said on Tuesday it had managed to get the first aid road convoy into Gaza City in the north of the Gaza Strip since February 20.
The charity ship Open Arms was seen sailing out of Larnaca port, towing a barge containing flour, rice and protein. The mission was funded mostly by the United Arab Emirates and organised by US-based charity World Central Kitchen (WCK).
The voyage to Gaza takes about 15 hours but a heavy tow barge could considerably lengthen the trip, possibly up to two days. Cyprus is just over 320 km northwest of Gaza.
The US military said one of its vessels, the General Frank S Besson, was also en route to provide humanitarian relief to Gaza by sea.
With aid agencies saying deliveries into Gaza have been held up by bureaucratic obstacles and insecurity since the start of the war on October 7, attention has shifted towards alternative routes including sea and air drops.
Qatar's foreign ministry spokesperson Majed Al-Ansari said on Tuesday that negotiators seeking a ceasefire between Israel and Palestinian Islamist group Hamas, which controls Gaza, were not close to a deal.
Washington had said for weeks that it hoped for a truce deal in time for the Ramadan Muslim holy month that began this week, but it has so far failed to materialise.
On Tuesday, US Central Intelligence Agency Director William Burns said there was "still a possibility" of a Gaza ceasefire deal, although many complicated issues remain.
Tuesday's sea supply mission was the culmination of months of preparation by Cyprus, the European Union member state closest to the conflict. It is keeping a wary eye on spillover effects from upheaval in the Middle East and is already seeing migratory inflows from Lebanon increasing. More than 400 people arrived in fishing boats on Monday.
Given the lack of port infrastructure in Gaza, WCK said it was building a landing jetty with material from destroyed buildings and rubble, an initiative separate to a plan announced by US President Joe Biden last week to build a temporary pier.
WCK Activation Manager Juan Camilo Jimenez told Reuters a second vessel would depart within the next few days.
The UN said such efforts can provide only limited relief as long as most land crossings to the coastal Palestinian enclave are completely sealed off by Israel, with "no meaningful substitute" on offer.
Israel says it is not to blame for Gaza's hunger, as it is allowing aid through two crossings at the southern edge of the territory. Aid agencies say that is not enough to get sufficient supplies through, particularly to the northern part of the enclave that is effectively cut off.
Gaza's health ministry said the number of Palestinians who have died of dehydration and malnutrition in the last two weeks had reached 27, after the deaths of two people on Tuesday.
The UN estimates a quarter of the 2.3 million population in Gaza is now at risk of starvation.
Fighters from Hamas, which administers Gaza, killed 1200 people in a lightning October 7 attack on Israel and took 253 hostages, according to Israeli tallies.
Israel's retaliatory military campaign has killed at least 31,184 Palestinians, according to Gaza authorities, and injured 72,889.
Ceasefire talks have so far failed to reach a breakthrough, with Israel saying it is interested only in a temporary truce to free hostages, and Hamas saying it will let them go only as part of a deal to permanently end the war.
