The military said in a statement that Sergeant Itay Hen, 19, "fell on October 7 and was then kidnapped" to the Hamas-ruled Gaza Strip by Palestinian militants.

The soldier, a dual Israeli-US national whose surname is also spelled Chen, was about one year into his military service in the Israeli Armoured Corps when his base near the Gaza border was attacked, his father, Ruby Chen, told reporters in October.

US President Joe Biden, who had met Chen's father and brother at the White House in December, expressed his condolences in a statement on Tuesday.

"Jill and I are devastated to learn that American Itay Chen was killed by Hamas during its brutal terrorist assault", Biden said.

"I reaffirm my pledge to all the families of those still held hostage: we are with you. We will never stop working to bring your loved ones home."

During the attack, Palestinian militants seized around 250 hostages, dozens of whom were released during a week-long truce in November.

Israel believes about 130 captives remain in Gaza, including 32 presumed dead.

The unprecedented October 7 attack resulted in the deaths of around 1,160 people in Israel, mostly civilians, according to an AFP tally based on Israeli figures.

Israel's retaliatory offensive in Gaza has killed 31,184 people, mostly women, children and adolescents, according to the latest toll from the Hamas-run territory's health ministry.