Israel's Supreme Court has approved the expulsion of relatives of a Palestinian militant from the West Bank to the Gaza Strip.

In a landmark ruling, a nine-judge panel upheld an order issued last month against the brother and sister of a Palestinian suspected of organising suicide bombings.

[The Ajouris] were involved in terrorism to the extent required such that they presented a reasonable possibility of danger

Israeli Supreme Court

It said a third Palestinian related to another militant suspected of two shooting attacks near a Jewish settlement in the West Bank should be set free.

Palestinian officials called the decision a "black day for human rights" and said they might file a complaint with the UN Security Council and the International Criminal Court.

The militant Palestinian group Hamas called the ruling a "grave escalation" which "will be met by an escalation in the Palestinian resistance".

The three accused had appealed against the order, saying it was a form of collective punishment and violated international law.

Israel said the move was intended to deter future attacks by Palestinian militants.

Militant helped

The Israeli army said the brother and sister - 28-year-old Kifah and 34-year-old Intisar Ajouri - knew in advance about their brother Ali's plan to carry out attacks but did not act to prevent them.

The two are accused of providing logistical support for their brother, helping him avoid capture and having moved bombs.

The Israeli army (IDF) said Ali Ajouri masterminded several suicide attacks, including one in Tel Aviv on 17 July, 2002, which killed five people and wounded 40 others.

The IDF said Intisar had sewn explosives into a belt used by a suicide bomber in one of the attacks.

Ali Ajouri was shot dead by Israeli troops on 6 August, 2002.

The court said that it "had proved that they [the Ajouris] were involved in terrorism to the extent required such that they presented a reasonable possibility of danger".

It ruled that the Ajouris could be expelled from their home in the Iskar refugee camp in Nablus to the Gaza Strip for two years.

But the judges overturned an expulsion order against Abdel Nasser Asidi, the brother a militant accused of two West Bank ambushes which killed 19 Israelis.

Burden of proof

In handing down the ruling, Chief Justice Aharon Barak said Israel could only expel a suspected militant's relative if they presented a real security threat.

The court ruled with a loud voice that deterrence cannot be a cause to take steps

Leah Tzemel, Ajouris' lawyer

Legal experts say the decision means Israel cannot expel people merely to deter future attacks, and that the army will have to provide proof of some form of involvement before it can issue expulsion orders.

"The court ruled with a loud voice that deterrence cannot be a cause to take steps. This is a very, very positive point," said the Ajouris' lawyer Leah Tzemel.

The order against the Ajouris has been condemned by human rights organisations, who say it contravenes the Geneva Conventions and therefore constitutes a war crime - a charge that Israel denies.

The judges said they had not breached international law because the West Bank and Gaza formed one territorial unit and the orders were relocations rather than expulsions.

If the expulsions are carried out it will be the first time Israel has expelled a Palestinian from the area in which they live for 10 years.