The US has charged Hamas leader Yahya Sinwar and several other prominent figures in the Palestinian group in connection with its deadly attack in Israel on 7 October last year.

The justice department said it was indicting six Hamas members with seven charges, including the murder of dozens of US citizens, conspiracy to finance terrorism and use of weapons of mass destruction.

The criminal complaint covers decades of alleged attacks by Hamas, as well as last October's unprecedented assault.

It is the first step by US law enforcement to hold accountable the ringleaders of that attack, but has been seen by analysts as partly symbolic, not least because some of those named in the indictment are already dead.

Meanwhile, Sinwar is believed to be hiding in tunnels somewhere under Gaza.

In a video statement on Tuesday, US Attorney General Merrick Garland said the defendants were responsible for "financing and directing a decades-long campaign to murder American citizens and endanger the security of the United States".

The group also "led Hamas's efforts to destroy the state of Israel and murder civilians in support of that aim", Mr Garland said.

He highlighted the 7 October attack on Israel by Hamas, in which the group "murdered entire families" in "the deadliest massacre of Jews since the Holocaust".

Mr Garland said: "They murdered the elderly and they murdered young children. They weaponised sexual violence against women, including rape and genital mutilation."

The charges were filed in February, but were kept under wraps until Tuesday in case the US had the opportunity to arrest any of the accused, an unnamed justice department official told CBS News, the BBC's US partner.

The justice department's complaint states that at least 43 American citizens were killed on 7 October.

The reason for the timing of the US charges was not immediately clear, although the recent discovery in Gaza of the body of an Israeli-American hostage - and five others - might have given the move "extra impetus", one analyst told the BBC.

The charges themselves were partly about the US sending "a message" to Hamas and anyone working with the group, added Prof Yossi Mekelberg, an associate fellow of the UK think tank Chatham House.

The message the US wanted to send was that "we'll pursue you dead or alive," Prof Mekelberg suggested.

In his comments, Mr Garland referred to the Israeli-American found dead in Gaza at the weekend, 23-year-old Hersh Goldberg-Polin, as well as the other American citizens killed or taken hostage in the 7 October attack.

“We are investigating Hersh’s murder, and each and every one of Hamas’ brutal murders of Americans, as an act of terrorism,” Mr Garland said.

President Joe Biden earlier condemned Goldberg-Polin's killing, too, calling it "as tragic as it is reprehensible".

“Make no mistake, Hamas leaders will pay for these crimes,” Mr Biden said.

The charges include conspiracy to bomb a place of public use resulting in death, conspiracy to finance terrorism and material support for acts of terrorism resulting in death.

If convicted, the group faces a maximum penalty of life in prison or a death sentence.

Alongside Sinwar, other Hamas leaders charged include former leader Ismail Haniyeh; Marwan Issa, the deputy leader of the organisation's armed wing; Khaled Mashaal, who leads the group outside Gaza and the West Bank; along with Mohammed Deif and Ali Baraka.

Haniyeh, Issa and Deif have all been reported killed in the past few months in attacks that were either claimed by or attributed to Israel.

The justice department’s complaint notes that all the “defendants are either deceased or remain at large”.

It remains to be seen whether the move will impact on the American efforts to urge Israel to agree a ceasefire and hostage-release deal with Hamas.

One US official anonymously told the Associated Press news agency that there was no reason to think the development would affect the ongoing talks.

But Prof Mekelberg felt it could affect Sinwar's mindset. “I don’t think this will be encouraging him to show flexibility,” he said.

In another new development related to the conflict in Gaza, the UK has defended its decision to ban some weapons sales to Israel over concerns about how they might be used in the Palestinian territory.

Hamas attacked southern Israel on 7 October, killing about 1,200 people and taking another 251 hostage.

More than 40,000 people have been killed in Gaza since then in Israel's ongoing military campaign, according to the territory's Hamas-run health ministry.