Israeli troops backed by helicopters have advanced into Gaza in the first ground action of an eight-day offensive against Hamas in the Palestinian enclave.

The small column of military vehicles crossed the boundary fence into northern Gaza under darkness.

At least seven people were reported killed by Israeli tank fire.

An Israeli military spokeswoman confirmed the incursion and said the aim was to seize areas from where Hamas was launching rocket attacks on southern Israel.

‘The objective is to destroy the Hamas terror infrastructure in the area of operations,’ Major Avital Leibovitch said.

Israel has also ordered the call-up of tens of thousands of military reservists as part of a ground offensive launched in Gaza, Prime Minister Ehud Olmert's office said in a statement.

It said that, in accordance with a secret cabinet discussion yesterday, the government ordered the armed forces ‘to draft the necessary reservists, on a scale of tens of thousands of troops’.

The United Nations Security Council is to hold a special meeting tomorrow on the crisis.

France condemned the ground offensive just hours after the Czech presidency of the European Union said the action was ‘defensive, not offensive’.

The conflicting statements suggested disunity among European partners ahead of separate visits to the region by French President Nicolas Sarkozy and an EU delegation led by Czech Foreign Minister Karel Schwarzenberg.

France, which handed the EU presidency to the Czechs on 1 January, has led calls for a ceasefire and hosted a meeting of EU foreign minsters to reinforce the message on Tuesday.

Israel steps up military campaign

Earlier, in the bloodiest incident of the day, an air strike on a mosque killed 11 Palestinian civilians, including children, and wounded dozens as they prayed, Hamas officials said.

An Israeli military spokesman had no immediate comment.

Israel has targeted mosques previously saying that Hamas had used them as command posts and fire bases.

Hamas kept up its rocket attacks on southern Israel in defiance of international calls for it to halt such actions.

As the Israeli offensive entered its second week, prospects of a ceasefire any time soon looked dim.

‘I hope the results of this operation will bring about quiet in the long term. The moment they fire, we will respond with great force,’ Foreign Minister Tzipi Livni said on Israeli TV.

The Palestinian death toll has risen to at least 446, with about 2,050 wounded, in the worst sustained bloodshed in decades of the conflict between Israel and the Palestinians.

Four Israelis have been killed in cross-border rocket attacks by Hamas and other militant groups.

Israeli air strikes targeted Gaza from early morning and naval vessels also shelled the area from the Mediterranean, witnesses said.

One strike killed Abu Zakaria al-Jamal, a senior commander of Hamas's armed wing, Hamas said. He was the second Hamas leader killed in three days.

Israeli war planes also hit a private Palestinian college called the American School, killing a guard.

Israel launched the campaign, called Operation Cast Lead, on 27 December saying it wanted to stop Hamas rocket attacks on southern Israel.

Israeli flag burned after protest

Protestors against the air attacks on Gaza have burnt an Israeli flag outside the Dáil.

Around 1,000 people attended the demonstration organised by the Ireland Palestine solidarity campaign.

The organisers say protests will take place as long as the Israeli bombardment continues and they called on the Government to boycott Israeli goods and businesses.

Afterwards around 80 protestors knelt on Kildare Street to pray.

In Galway city, around 250 people protested against Israel's actions in Gaza and called for the bombardment to end.

Bush says Hamas is responsible

Amid growing concern for the humanitarian condition in the densely-populated territory, the US gave its close ally free rein to push on with a ground offensive, insisting that the key to a ceasefire is Israel's demand for Hamas to permanently halt rocket fire.

US President George W Bush urged all able parties to press Hamas to stop firing on Israel to facilitate a lasting ceasefire.

'The United States is leading diplomatic efforts to achieve a meaningful ceasefire that is fully respected,' Mr Bush said in his weekly radio address to be broadcast today, the text of which was released late yesterday.

'I urge all parties to pressure Hamas to turn away from terror, and to support legitimate Palestinian leaders working for peace.'

Mr Bush said Hamas was responsible for the latest violence and rejected a unilateral ceasefire that would allow Hamas to continue to fire on Israel.

'This recent outburst of violence was instigated by Hamas - a Palestinian terrorist group supported by Iran and Syria that calls for Israel's destruction,' Mr Bush said.

Hamas's Syrian-based chief Khaled Meshaal, meanwhile, told Israel that 'if you commit the stupidity of launching a ground offensive then a black destiny awaits you.

'You will soon find out that Gaza is the wrath of God,' Mr Meshaal said in pre-taped remarks as the death toll rose from bombing and concerns grew about the humanitarian situation in the Palestinian territory.