Boston (AFP): US President Joe Biden called on Tuesday for global condemnation of what he said was "horrific" sexual violence by Hamas during the October 7 attacks on Israel.

Biden's comments come after campaigners in Israel have derided what they see as a muted international response to gender-based violence during the attack.

"The world can't just look away at what’s going on," Biden said at a campaign event in Boston.

"It’s on all of us -- government, international organizations, civil society and businesses -- to forcefully condemn the sexual violence of Hamas terrorists without equivocation."

Biden said there had been reports that Hamas "used rape to terrorize women and girls" during the attacks last month, in which Israel says 1,200 people were killed.

"Over the past few weeks, survivors and witnesses of the attacks have shared the horrific accounts of unimaginable cruelty," including rape, mutilation and the desecration of bodies, he said.

"Hamas terrorists inflicting as much pain and suffering on women and girls as possible and then murdering them -- It is appalling."

In response to the Hamas attack, Israel vowed to destroy the group and has carried out air strikes and a ground offensive that have killed more than 16,200 people, mostly women and children, according to Gaza's Hamas-run government.

Israeli women and legal activists have accused international rights groups of maintaining a conspiracy of silence over alleged rapes and other sexual crimes during the October 7 attacks.

The UN secretary-general and UN Women issued statements on the allegations only last week, despite Israeli activists sending letters to UN agencies shortly after the attacks.

Campaigners say the responses were minimal, leaving them deeply frustrated and accusing the global human rights community of betrayal.

In Israel, senior police officer Shelly Harush told lawmakers last week that investigators had collected "more than 1,500 shocking and difficult testimonies" from witnesses, medics and pathologists.

A US State Department spokesman said on Monday that Hamas likely held back on freeing female hostages because it did not want the women to speak publicly about sexual violence.

Hamas said on Monday that the allegations of sexual assault were part of "Zionist campaigns which promote unfounded lies and allegations to demonize the Palestinian resistance."

Biden meanwhile called for Hamas to release female hostages it is still holding in Gaza, saying the group's refusal to free them had led to the breakdown of a truce with Israel.

Biden said that Hamas had "refused to let go" a number of women aged between 20 and 39 under the deal brokered by Qatar between Israel and the Palestinian group.

"These women and everyone still being held hostage by Hamas need to be returned to their families immediately. We’re not going to stop until we bring every one of them home and it’s going to be a long process," he said.