Israel's crippling blockade of the Gaza Strip is a collective punishment of the 1.5 million population of the small, overcrowded territory, Human Rights Watch said in its annual report on Thursday, January 31.

"The Israeli and Western economic embargo of Gaza, Israel's almost total closure of Gaza's border crossings, ongoing lawlessness in the Occupied Palestinian Territories, and heightened Israeli restrictions on freedom of movement in the West Bank contributed to a serious human rights and humanitarian crisis," said the report cited by Agence France-Presse (AFP).

It said Israel's decision to halt shipments of food, fuel and medical supplies constituted "collective punishment of Gaza's civilian population in violation of international humanitarian law."

Israel's Supreme Court on Wednesday backed Defense Minister Ehud Barak's decision.

Israel has progressively tightened restrictions on movement in and out of Gaza since June 2006, leaving Rafah border crossing -- Gaza's only one that bypasses Israel -- closed almost continuously.

"The general population has borne the brunt of Israel's measure," said the HRW.

Gaza lockdown has triggered a severe humanitarian crisis, forcing hundreds of thousands of people to storm the closed borders with Egypt to stock up on desperately-needed supplies.

The New York-based rights watchdog denounced the impunity enjoyed by Israeli soldiers who killed Palestinians.

"The Israeli army's continued failure to investigate civilian death and injury where there was evidence of a laws of war violation reinforces a culture of impunity in the army and robs victims of an effective remedy," it said.

At least 145 Palestinians have been killed by Israeli soldiers since the US-hosted Annapolis peace conference in November.

Israeli soldiers killed a Palestinian resistance activist in southern Gaza on Thursday, January 31.

HRW said Israel continued to restrict freedom of movement in the West Bank and Al-Quds (occupied East Jerusalem) and expand "illegal settlements" in the West Bank.

"Settler violence against Palestinians and their property continues with virtual impunity."

HRW said that despite Israel being by far the largest recipient of American aid, the US had "not made the funding conditional on Israel improving its human rights record."

The rights watchdog blamed Palestinian infighting for worsening the suffering of the civilian population.

"Palestinian armed groups, rival security forces, and powerful clans continue armed attacks on one another," it said.

HRW noted the worst violence was last June between rival Hamas Fatah of President Mahmoud Abbas, which killed more than 160 people and left Hamas in control of the Gaza Strip.

The group accused both sides of "unnecessarily endangering civilians by deploying in populated areas during the fighting and blocking the access of medical teams to injured persons."

HRW said neither Hamas nor the Ramallah-based Palestinian Authority made "efforts to investigate these crimes or hold anyone to account, further entrenching impunity."