AIRO, July 8 (Reuters) - A new Israeli assault on Gaza on Monday threatened ceasefire talks at a crucial moment, the head of Hamas said, as Israeli tanks pressed into the heart of Gaza City and ordered residents out after a night of massive bombardment.
Residents said the airstrikes and artillery barrages were among the heaviest in nine months of conflict between Israeli forces and Hamas militants in the enclave. Thousands fled.
The assault unfolded as senior U.S. officials were in the region pushing for a ceasefire after Hamas made major concessions last week. The militant group said the new offensive appeared intended to derail the talks and called for mediators to rein in Israel's Prime Minister Benjamin Netanyahu.
The assault "could bring the negotiation process back to square one. Netanyahu and his army will bear full responsibility for the collapse of this path," Hamas quoted leader Ismail Haniyeh as saying.
Gaza City, in the north of the Palestinian enclave, was one of Israel's first targets at the start of the war in October. But clashes with militants there have persisted and civilians have sought shelter elsewhere, adding to waves of displacement. Much of the city lies in ruins.
Residents said Gaza City neighbourhoods were bombed through the night into the early morning hours of Monday. Several multi-storey buildings were destroyed, they said.
The Gaza Civil Emergency Service said it believed dozens of people were killed but emergency teams were unable to reach them because of ongoing offensives.
Gaza residents said tanks advanced from at least three directions on Monday and reached the heart of Gaza City, backed by heavy Israeli fire from the air and ground.
That forced thousands of people out of their homes to look for safer shelter, which for many was impossible to find, and some slept on the roadside.
