Israeli tanks and armored vehicles are re-occupying an area in northern Gaza, one day after the Israeli government said it would create a buffer zone in the region, BBC reported.

On Wednesday, Israel vowed to intensify attacks on the Hamas-led Palestinian government, whose armed wing is part of three groups holding Israeli soldier Gilad Shalit, who was captured on June 25.

Prime Minister Ehud Olmert authorized Israeli troops to move into densely populated residential areas in Gaza and create a "security zone" in the north, raising the possibility of an extended military presence in the area.

Israel claims that the latest measures are aimed at stopping Palestinian resistance fighters from firing rockets into Israel after two Palestinian missiles struck the Israeli city of Ashkelon.

There were no injuries reported in the two Palestinian attacks, both claimed by the armed wing of Hamas, which said that the rockets were an upgraded version of an older Qassam model that can hit targets up to 15 km away.

Palestinian witnesses said more than 15 Israeli tanks entered the area in northern Gaza, which houses the former Gaza settlements of Nissanit, Dugit, and Elei Sinai that were evacuated last year when Israel withdrew all its troops and settlers from the coastal strip.

The Palestinian Health Ministry said 17 Palestinians, including many civilians, were killed and more than 55 wounded in Gaza since midnight local time. 

Reports say one of the deadliest incidents was in the northern Gaza town of Beit Lahiya, which witnessed fierce clashes between Israeli troops and Palestinian fighters. 

Medics said the fighting killed more than five Palestinians, including civilians, and an Israeli soldier.

According to BBC, many Palestinian residents have left northern Gaza when they saw Israeli troops approaching at dawn.

• In other developments:

• Israeli police arrested five top Hamas members in Jerusalem, claiming that they had been helping Hamas lawmakers conduct party activity in the city

• Israel closed the main goods crossing point with Gaza

• In southern Gaza, Israeli aircraft attacked a group of Palestinian fighters, killing more than two people and injuring several others, including civilians.

• Earlier, two Hamas fighters and a policeman were killed when Israeli artillery pounded the northern Gaza Strip.

Israel began an extensive offensive in Gaza - its biggest military operation in a year - claiming that it's aimed at securing Shalit's release.

But there is a widespread belief among Gaza's 1.4 million residents that the Israeli army will attack whether or not the Israeli soldier is released.

"What the Israelis are trying to do is dismantle the Hamas government and kill the people's democratic choice. This will plant violence in everybody's heart. People have tried democracy in order to live in dignity," said the Hamas' mayor of the northern Gaza town of Beit Hanoun.

• UN condemnation

The UN Human rights watchdog passed a resolution denouncing Israel's offensive in Gaza as a violation of international law.

The resolution, proposed by Muslim states, expressed "grave concern at the violations of the human rights of the Palestinian people caused by the Israeli occupation, including the current extensive Israeli military operations".

The Council also demanded "Israel, the occupying power, to immediately release the arrested Palestinian ministers... and all other arrested Palestinian civilians".

It also called "for a negotiated solution to the current crisis", and said that it would send a fact-finding mission to investigate Israel's human rights violations in the occupied Palestinian territories.

The latest developments come amid growing concern among aid agencies over the deteriorating humanitarian situation in Gaza.

The United Nations has warned of an imminent humanitarian crisis in the region. Unicef has seen increased levels of stress and trauma among young children, and the World Health Organization says basic medical supplies are running short and doctors and nurses are having great difficulty even getting to work because of Israel's restrictions on movement.