The international community voiced grave concerns Saturday over Israel's ground troops invasion against the Gaza Strip following eight days of intensive airstrikes on the volatile region.

UN Secretary-General Ban Ki-moon Saturday expressed his extreme concern and disappointment at the Israeli invasion, calling for "an immediate end" to the military operation, a UN statement said on Saturday.

It said that the UN chief "asked that Israel do all possible to ensure the protection of civilians and that humanitarian assistance is able to reach those in need."

"The secretary-general has spoken with (Israeli) Prime Minister Olmert and conveyed his extreme concern and disappointment," the statement said.

The United States is deeply concerned over the humanitarian situation in the Gaza Strip and urged Israel to avoid causing civilian casualties during its military strikes against Palestinian militants, the US State Department said.

"Any military action needs to be mindful of the potential consequences to civilians, " said Sean McCormack, the State Department spokesman.

France said the military action had complicated efforts by the international community to find a truce in the region.

"France condemns the Israeli ground offensive against Gaza as it condemns the continuation of rocket firing (by Islamic Resistance Movement,or Hamas, against Israel)," the French Foreign Ministry said in a statement.

In a presidential statement, Egypt called on Israel to stop its attacks against Gaza "immediately".

Egypt also urged the UN Security Council and the international Quartet on Mideast peace to intervene to help halt the Israeli attacks, the statement said.

Jordan's King Abdullah II called for global efforts to pressure Israel to stop aggression in the Gaza Strip, said the Royal Hashemite Court on Saturday.

Abdullah said the humanitarian situation in Gaza had deteriorated to an extent that could not be tolerated.

On Saturday, Israel's ground troops entered the Gaza Strip ruled by Islamic Resistance Movement (Hamas) for the second phase of offensive on the militant group after a week of airstrikes.

Israel vowed to destroy "terror infrastructure of Hamas as its Cast Lead operation starting last Saturday is now entering its second stage."

About 20 Palestinians, including militants and civilians, were killed Saturday evening during Israel's ground invasion in Gaza, said Hassan Khalaf, an official at Shifa hospital in Gaza City.

Israel's military action, aimed at retaliating for Hamas militants' rocket attacks into Israel, has killed at least 460 Palestinians and wounded 2,750 others in the past week.

Israeli Defense Minister Ehud Barak said Saturday evening that Israel Defense Forces (IDF) operation against Palestinian militants in the Hamas-controlled Gaza Strip would be neither short nor easy.

He said that Israel was not eager to wage war, but could not abandon its citizens and residents in the south, who had been victimized by Hamas rockets.

"The campaign won't be easy and it won't be short," he said, noting that the operation entailed the risking of Israeli lives. "I know well the dangers that come with an offensive, and what the heavy price will be."

"I don't want to fool anyone. The residents of southern Israel will also undergo some tough times," he said.

Palestinian Islamic Hamas movement vowed on Saturday to hit back Israeli army's ground operation with heavy blow.

"The enemy will pay a high price for its operation in northern Gaza Strip," Hamas military wing Ezzedine Al-Qassam Brigades said in a statement.

Riyad Mansour, permanent Palestinian observer to the United Nations, Saturday urged the UN Security Council "to send a very strong message" to Israelis and demand "an immediate ceasefire" in the Gaza conflict.

(Xinhua News Agency January 4, 2009)