US Ambassador to Israel Mike Huckabee says he has asked Israeli authorities to "aggressively investigate" the killing of a Palestinian-American in the occupied West Bank.

Sayfollah Musallet, known as Saif - a 20-year-old dual US citizen from Florida - was beaten to death by Israeli settlers in the town of Sinjil on Friday evening, according to the Palestinian health ministry.

After an initially muted official US reaction to the killing, Huckabee - a longstanding supporter of Israeli settlements in the Palestinian territories - described it as a "criminal and terrorist act" on Tuesday.

"There must be accountability," he wrote in a post on X. "Saif was just 20 years old."

On Friday, the Israeli military said it was investigating, claiming that a "violent confrontation developed" after "terrorists" threw stones at Israeli civilians.

Saif Musallat lived in Tampa and was visiting relatives in Sinjil, north of Ramallah, when he was killed along with his friend, Mohammed al-Shalabi.

Al-Shalabi, who lived in a town nearby, died after being shot in the chest, the Palestinian health ministry said. He was 23 years old.

Musallat's family said their relative was "protecting his family's land from settlers who were attempting to steal it".

Israeli settlers also blocked an ambulance attempting to reach Musallat, who died before he could make it to hospital, they added.

The family have called for the US state department to carry out an investigation.

Huckabee, a former governor of Arkansas and evangelical Christian, has previously voiced strong support for Israeli settlements - which are seen as illegal under international law.

Huckabee has also been criticised by opposition Democrats in the US over his previous statements about the ongoing war in Gaza.

He has backed the idea of a "greater Israel" - where Israel would have permanent control of the Occupied Palestinian Territories - and used the biblical term "Judea and Samaria" to refer to the West Bank.

Last month, he criticised US allies, including the UK and Australia, for sanctioning two far-right Israeli ministers over "repeated incitements of violence against Palestinian communities" in the West Bank.