Lebanon's government was plunged into crisis last night after five cabinet members resigned in what appeared to be an attempt by Hizbollah, the Shia militant group, to cause its collapse.

Fouad Siniora, the prime minister, attempted to hold his government together by refusing to accept the resignations.

  
Lebanon's prime minister Fouad Siniora
But Hizbollah piled on pressure by announcing street demonstrations this week to force the government to accede to the group's demands for greater cabinet representation.

Sheikh Naim Kassem, Hizbollah's deputy leader, said that the resignations were the first step in a campaign that would be "varied and effective".

Fears of bloody confrontations were raised as members of the ruling coalition promised counter-demonstrations.

All-party talks aimed at averting the crisis collapsed in Beirut on Saturday after Mr Siniora's allies rejected demands by Hizbollah and its allies for representation that would have given them sufficient power to veto key legislation.
The talks had been aimed at easing mounting sectarian tensions in the aftermath of the 34-day war between Hizbollah and Israel.

Hours after the talks broke down, the five cabinet ministers representing Hizbollah and its Shia ally, the Amal movement, resigned. They included Fawzi Salloukh, the foreign minister, as well as the ministers for agriculture, health, energy and labour. Under the Lebanese constitution, if eight ministers resigned, the government would have to be dissolved.

The Lebanese president, Emile Lahoud, said that the resignation of all the ministers from the country's largest religious faction meant any decisions made by the cabinet were invalid.

However, as things stand, he does not have the power to dissolve the government.

Mr Siniora's supporters claimed that pro-Syrian groups wanted the talks to fail to thwart the creation of an international tribunal into the assassination of Rafik Hariri, the former prime minister, last year.

The killing led to mass anti-Syrian protests in Lebanon, which decided Damascus to end its 29-year military presence in the country and prompted new elections.

On Friday, Mr Siniora received a proposed framework for the Hariri tribunal from the United Nations, and he had invited the cabinet to a special meeting today to endorse it. Last night he said the meeting would go ahead as planned.

Senior Syrian security officials have been widely implicated in the killing, although Damascus denies involvement.

Condoleezza Rice, the American secretary of state, said during the weekend that Syria was a dangerous state whose territory was being used for the accelerated arming of Hizbollah.

A group identifying itself as "al-Qa'eda Lebanon" added to concerns by threatening to destroy the government, saying that it was corrupt and took orders from the American administration.