Israeli officials say vigilance prevented a higher casualty toll

Two guards were seriously injured in the morning rush hour blast. It was the first such attack since Israel pulled its settlers out of the Gaza Strip.

Palestinian leader Mahmoud Abbas, condemning the attack, described it as a "terrorist operation".

But he also described a recent Israeli raid in the West Bank in which five Palestinians died as a "provocation".

The Islamic Jihad group had sworn to take revenge for the deaths.

Israel warns Palestinians

A bus driver told Israel Radio that the suicide bomber was carrying a heavy bag, prompting him to alert a security guard. Before he could get on the bus he was stopped, and he blew himself up nearby, according to police.

A paramedic covered the dead bomber's head with a bag

The two security guards who were critically wounded suffered shrapnel wounds and burns all over their bodies, a paramedic told Israel's Channel 10 TV.

The bomber's remains were scattered at the scene.

The last serious bomb attack in Israel was in the coastal city of Netanya on 12 July, when five people were killed.

Beersheba was hit almost a year ago, when twin bus blasts in the city killed 16 people. Those attacks were claimed by Palestinian Hamas militants.

Speaking after Sunday's blast, a spokesman for Prime Minister Ariel Sharon said "Israel has taken the necessary steps to further the prospects of peace with the Palestinians."

The bombing, said spokesman David Baker, "is another indication that the Palestinian Authority must take proper steps against terror, and without these steps, there will be no progress between both sides".

Mr Abbas said in a statement that it was vital everyone remain committed to the truce, "despite all the Israeli provocations, most recently the killing of five Palestinians in Tulkarem, among them three children".

Israel says the five men killed in the West Bank raid were militants wanted in connection with suicide bombings.

'Fire with fire'

Hamas has said attacks on Israel must continue, despite the withdrawal of Jewish settlers from the Gaza Strip.

Mr Sharon told Israelis at the time that while the withdrawal was a risky manoeuvre, it was the best way to ensure security in the longer term.

But he also gave stark warnings on how Israel would respond if it appeared that the Palestinians were failing to crack down on extremist groups.

"To an outstretched hand we shall respond with an olive branch," he said, "but we shall fight fire with the harshest fire ever."