Four Palestinian civilians were killed and nine Hamas militants were injured during Israeli ground operation in the Gaza Strip on Saturday evening, Palestinian hospital sources said.

The sources at the Shifa Hospital in Gaza City said that four Palestinian civilians were killed in Israeli tank shelling on Gaza Strip while nine Hamas militants were injured during exchange of fire with Israeli army.

Israel troops entered Gaza Strip on Saturday evening, launching ground invasion against the coastal area.

The Palestinian Hamas movement, which rules Gaza, said armed clashes and exchanges of fire were taking place in northern and eastern Gaza Strip between Israeli soldiers and Gaza militants.

The movement said in a statement sent to reporters that heavy and tough exchange of fire and armed clashes took place between Gaza militants and the invading Israeli army ground forces.

It said that fighters of Hamas armed wing al-Qassam Brigades and fighters from other Palestinian factions are "confronting with the Israeli army ground forces, which entered into the Gaza Strip territory early on Saturday evening."

"The Israeli army forces are slowly entering into the area because of the heavy gunfire of the Palestinian resistance," Hamas said, adding "there are some Israeli soldiers are either killed or wounded."

No confirmation was available from the Israeli army to confirm or deny Hamas reports on casualties among the Israeli soldiers.

Hamas has earlier warned Israel on Saturday night of carrying out a large-scale military operation into the Gaza Strip that it has been ruling since June 2007.

Hamas armed wing Al-Qassam Brigades said in a statement sent to reporters that "Al-Qassam brigades declare that the Zionist enemy is getting close to the trap that our fighters had prepared for its soldiers and tanks."

The group added "the Zionist enemy would see surprises and would regret carrying out such an operation and will be a heavy price. Our militants are waiting with patience for confronting the soldiers face to face."

Israel's ground operation started following eight days of intensive airstrikes on the 1.5 million population of the enclave, targeting buildings, including mosques, houses and Hamas security installations.

(Xinhua News Agency January 4, 2009)