Israel attempted to kill the political leaders of Hamas with an airstrike on Doha on Tuesday, in what US officials described as a unilateral escalation that did not serve American or Israeli interests.

In a televised address, Hamas official Fawzi Barhoum said the strike targeted the group’s negotiating delegation while they were discussing a new ceasefire proposal delivered by the Qatari prime minister just a day earlier.

“At the moment of the terrorist attack, the negotiating delegation was in the process of discussing its response to the proposal”, he said.

Qatar has been hosting and mediating in negotiations aimed at securing a ceasefire in the Gaza war.

Barhoum reaffirmed Hamas’s key demands: a full ceasefire, the withdrawal of Israeli forces from Gaza, a real prisoner-for-hostage exchange, humanitarian relief and reconstruction of the enclave.

Israeli Prime Minister Benjamin Netanyahu is pushing for an all-or-nothing deal that would see all of the hostages released at once and Hamas surrendering.

Hamas said five of its members had been killed in the attack, including the son of Hamas’s exiled Gaza chief and top negotiator Khalil al-Hayya.

The attack on Doha drew condemnation from regional powers, including Saudi Arabia and the United Arab Emirates, as well as the European Union, and risks derailing U.S.-backed efforts to broker a truce and end the nearly two-year-old conflict.