Fighting in the Gaza Strip escalated on Thursday with some of the most intense Israeli bombardment of the war and Hamas demonstrated its ability to rocket Tel Aviv, even as the enemies held their most serious talks for weeks on a new truce.

Israeli bombing was at its most intense over the northern part of the Gaza Strip where orange flashes of explosions and black smoke could be seen as morning broke from across the fence in Israel. Planes roared overhead and the booms of air strikes thundered every few seconds, punctuated by rattling gunfire.

In Israel’s commercial capital Tel Aviv, sirens wailed and rockets exploded overhead, intercepted by Israeli defences. Israel’s Magen David Adom ambulance service said there were several impact points but no initial word on casualties.

The armed wing of Hamas said it had fired the salvo in response to Israeli killing of civilians. But with the group’s leader in Cairo for truce talks, the attack seemed clearly timed to send a diplomatic message that 10 weeks of war that has laid waste to much of Gaza had failed to destroy the militants’ strike capability.

Residents in Jabalia in the north of the Strip close to the Israeli border said the area was completely cut off with Israeli snipers now firing on anyone trying to escape.

“It was one of the worst nights in terms of the occupation bombings. Also we could hear heavy fighting despite that,” said one Jabalia resident who asked not to be identified for fear of reprisal.

With Gaza’s communications links shut down for a second day, the resident spoke to Reuters by phone using an electronic SIM card to access the Israeli mobile network across the fence. Gazans say such cuts to communication links have typically heralded Israeli assaults.