Israel rushed an eighth missile interceptor battery into service yesterday to counter stronger-than-expected rocket fire from Gaza as the military pounded positions in the Palestinian enclave for a fifth day, killing 15 people, medics said.

The Jewish state kept options open for a possible ground offensive into densely populated Gaza despite international pressure to negotiate a ceasefire in the conflict, which has killed 121 in the Islamist-ruled enclave since Tuesday.

Residents said a mosque in the central Gaza Strip was bombed to rubble. The Israeli military said the mosque had housed a weapons cache. Referring to Israel’s Prime Minister, graffiti scrawled on one of the mosque’s blasted walls read, “We will prevail despite your arrogance, Netanyahu”.

Eight other mosques have been damaged from bombing and 537 Gaza houses have either been destroyed or damaged, according to the Gaza-based Al-Mezan Association for Human Rights.

Up to yesterday, no Israeli had been killed by rockets salvoes out of Gaza, thanks in part to Iron Dome, a partly US-funded interceptor system that operators said had exceeded expectations in shooting down missiles.

Women hoping to cross into Egypt present their passports as they wait at the Rafah crossing between Egypt and the southern Gaza Strip yesterday. Egyptian authorities had decided to open the Rafah border crossing to Gaza to allow wounded Palestinians to receive medical care in Egypt.

But racing for shelter from rockets has become a daily routine for hundreds of thousands of Israelis, and some 20,000 reservists have already been mobilised for a possible thrust into Gaza.

“We have upgraded the (Iron Dome) system recently from a number of aspects. We try always to be one step ahead of the enemy and we see that its capabilities exceed our expectations,” a defence ministry official said.

“In the past week we have carried out a very complex technological exercise to deliver the eighth system. We brought together all the components from the production line and within days we made it operational,” he added, saying that a ninth battery could be made ready within days.

Israel said it was determined to end cross-border rocket attacks that intensified last month after its forces arrested hundreds of activists from the Islamist Hamas move­ment in the West Bank after the abduction there of three Jewish teenagers who were later found killed. A Palestinian youth was then killed in Jerusalem in a suspected revenge attack by Israelis.

Gaza medical officials said at least 81 civilians, including 25 children, were among the 121 dead so far from aerial strikes on the sliver-like territory into which nearly two million people are packed, many in dilapidated dwellings.