Militant groups in Gaza said they have joined forces to step-up attacks against Israel, possibly including suicide bombings.
A spokesman for Hamas, which controls Gaza, said 13 militant groups would work together to launch 'more effective attacks' against Israel.
Asked if this included suicide bombings, he said: 'All options are open.'
The statement was made as Israeli and Palestinian leaders agreed in Washington to a series of direct talks, seeking to forge the framework for a US-backed peace deal within a year and end a conflict that has boiled for six decades.
Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas held the first round of face-to-face Israeli-Palestinian talks in 20 months with the goal of reaching a final peace deal envisaging a Palestinian state within a year.
Hamas has claimed responsibility for two separate shooting attacks in the occupied West Bank this week that killed four Israeli settlers and wounded two.
And last night in Gaza, several armed gunmen held an open-air news conference where Abu Ubaida, a spokesman for Hamas's military wing, vowed that militants would 'respond to the negotiations that aim at selling out (Palestinian) land'.
The 13 armed groups also include Islamic Jihad, the Popular Resistance Committees and a splinter armed group from Abbas's Fatah movement.
'We declare that the actions of resistance have gone into a new and advanced stage of cooperation in the field at the highest levels in preparation for more effective attacks against the enemy,' Abu Ubaida said.
