Three Israeli hostages mistakenly killed by Israeli soldiers in Gaza were shot dead while holding a white cloth, an Israeli military official says.

The official said the case was "against our rules of engagement" and an investigation was happening at the "highest level".

The hostages - Yotam Haim, 28, Samer Talalka, 22, and Alon Shamriz, 26 - were killed in Shejaiya on Friday.

Israeli troops have been facing stiff resistance in the area near Gaza City.

The case will add pressure on Israeli authorities to reach a deal for the release of captives who remain in Gaza.

More than 120 people remain hostage in Gaza, after being abducted in the Hamas attacks on October 7.

Prime Minister Benjamin Netanyahu told a news conference on Saturday evening that there would be no let-up in the Israeli operations.

"Military pressure is necessary both for the return of the hostages and for victory. Without military pressure... we have nothing," Mr Netanyahu said.

An Israeli military official, who spoke on condition of anonymity, said an initial investigation by the Israel Defense Forces (IDF) suggested the three hostages emerged shirtless from a building, with one carrying a stick with a white cloth.

One of the soldiers, the official added, felt threatened, as the men were at a distance of tens of metres, declared them "terrorists" and opened fire. Two were immediately killed while the third, wounded, returned to the building.

A cry for help was heard in Hebrew and the battalion commander ordered the troops to cease fire. The wounded hostage later re-emerged, and was shot and killed, the official said.

The hostages had either been abandoned by their captors or escaped, the official added.

Meanwhile, a freed Thai hostage who was held with the three men recalled his time with them.

Wichian Temthong, 37, said he was "very shocked" and "saddened" to learn of the deaths of the men he spent nearly 50 days in captivity with.

He said they had no common language so they used hand signals to communicate and give each other moral support.

In Tel Aviv, relatives of the hostages who are still being held in Gaza are expected to react to the incident later on Saturday outside the city's Museum of Art, in what is now known as Hostages Square.

Since the end of a temporary ceasefire between Israel and Hamas earlier this month, the families have urged the Israeli government to reach a new truce for at least some of the captives to be freed. The initial deal led to the release of more than 100 hostages, in exchange for Palestinians held in Israeli jails.

"The Israeli government should make Hamas an offer they can't refuse. A ceasefire, an exchange, whatever it takes. The government has done nothing," Lior Peri, whose 79-year-old father Haim remains a hostage, told the BBC.

"It's a rollercoaster [of emotions]. Every time we think we've reached a new low - but we can only imagine what's happening to the remaining hostages."

The war in Gaza, launched in response to the Hamas attacks that killed around 1,200 in Israel, has killed more than 18,000 people, according to the local health authorities, and pushed hundreds of thousands of others from their homes.

Vast areas of the territory have been destroyed, and the United Nations has warned of a humanitarian catastrophe amid widespread shortages of basic supplies.

Israeli authorities say the offensive's goal is to destroy Hamas and release the hostages.

Amid mounting Palestinian civilian casualties, Israeli authorities have come under growing international pressure, including from the country's main ally, the US, but they have resisted calls for a ceasefire.

Mr Netanyahu deflected the pressure again on Saturday.

"Despite grief, despite international pressure, we continue until the end, nothing will stop us," he said.