Two gunmen attacked a bus station and the offices of Israel's governing Likud party in the northern town of Beit Shean on Thursday afternoon, killing six.

The Likud offices were packed with party members voting in a leadership election that pits Prime Minister Ariel Sharon against Foreign Minister Binyamin Netanyahu.

Some of the wounded were airlifted to hospital in Haifa

Four Israelis were killed at the scene of the attack, with two later dying in hospital. Dozens of people were injured, including three children of former Foreign Minister David Levy, according to the Israeli daily Haaretz.

The al-Aqsa Martyrs' Brigade, a Palestinian group connected to Yasser Arafat's Fatah movement, has claimed responsibility for the attack in statements released to foreign media.

However, the Palestinian Authority later condemned the attack.

"We strongly condemn the operation in Bet Shean against Israeli civilians," the authority said in a statement quoted by AFP news agency. "This operation will not help the Palestinian people and its cause."

The group said it was taking revenge for the deaths of two commanders in Jenin refugee camp, which is close to Beit Shean, on Tuesday.

'Hundreds of bullets'

An eyewitness living near the Likud offices, Galit Cohen, told Israeli army radio that one of the gunmen laughed as he sprayed people with automatic fire.

"I opened the window and I simply saw the terrorist standing, smiling, laughing and shooting in all directions.

Netanyahu says he can still win

"He simply shot and shot and shot and he didn't stop. People were fleeing and falling."

Beit Shean's mayor, Pini Caballo, said the gunmen had fired "hundreds of bullets" and witnesses heard at least two grenade blasts.

The BBC's James Rodgers reports that Israeli sappers have been trying to make safe a belt of explosives worn by one of the attackers which failed to detonate.

Security issue

Security is a leading issue in Thursday's vote - which is already being overshadowed by the attack against an Israeli-owned hotel in Kenya earlier in the day.

Prime Minister Sharon is fending off a challenge from his Foreign Minister, Mr Netanyahu, two months before a general election.

Mr Sharon is portraying himself as a national father figure and the voice of moderation on the Palestinian issue, while Mr Netanyahu says he will never agree to the creation of a Palestinian state.

More than 300,000 Likud members are eligible to vote at 678 polling stations. Exit poll results are due to be released immediately after balloting ends at 2200 (2000GMT).

Final opinion polls gave Mr Sharon a commanding lead of over 20%, but Mr Netanyahu has accused pollsters of exaggerating the difference between them.

A third candidate, Moshe Feiglin - who has advocated a Jewish "holy war" - is expected to win no more than 2%.

The winner will become the favourite to be prime minister after a general election due on 28 January.

State 'inevitable'

A central platform of Mr Netanyahu's campaign is a pledge to send Palestinian leader Yasser Arafat into exile.

This, he says, is the first thing he will do if elected.

Opinion poll

Sharon: 61% Netanyahu: 37% Feiglin: 2% Source: Haaretz newspaper

Mr Netanyahu, himself a former Likud Prime Minister, has compared Mr Arafat's Palestinian Authority to Afghanistan's Taleban.

The clearest policy difference between the rival contenders is over Mr Netanyahu's opposition to the creation of a Palestinian state.

The BBC's Jeremy Cooke in Jerusalem says Mr Sharon is no enthusiast for the idea. But he has, it seems, come to see such a development as almost inevitable.

"I don't think there is one statesman who would oppose such a state," Mr Sharon told Maariv earlier this week.