A spokesman for Hamas said the Palestinian military group was prepared to kill hostages taken during a surprise attack on Israel over the weekend.

Abu Obaida, representing the armed wing of Hamas, said on Al Jazeera the group would kill one hostage an hour should Israel strike civilian homes in Gaza without warning.

The assault by Hamas has killed more than 900 Israelis, mostly civilians. Nearly 700 Palestinians have been killed during retaliatory strikes.

Read more: The latest rolling coverage of the Israel-Hamas war

With the conflict nearing its fourth day, the violence is showing no signs of abating and the rhetoric has escalated.

The exact number of hostages is not known but Israeli officials have spoken of there being dozens. Their precise whereabouts is also not clear although Hamas has said they have been spread throughout Gaza.

Israel’s military traditionally instructs civilians to evacuate before it hits apartment or office towers in Gaza where civilians might be present. But buildings are now being hit without warning, according to Gaza residents.

Israeli Prime Minister Benjamin Netanyahu has said his country is at war, warning that “what Hamas will experience will be difficult and terrible; we are already in the campaign and we are just getting started.”