This morning, the rival sides exchanged gunfire in two villages in eastern Lebanon's Bekaa valley, with three people reported injured, according to security forces.

Fighting yesterday had been confined to Beirut, with scores of gunmen from both sides clashing in several mixed Shia and Sunni areas of the city and at least 10 people reported as wounded. The Lebanese army was deployed but used no force.

This week's fighting – the latest flare of violence in a long disagreement between the Iranian and Syrian-backed militia and the US-supported government – was triggered on Tuesday when Lebanon's cabinet said Hizbullah's communication network was "an attack on the sovereignty of the state".

Hizbullah said the network was part of its security apparatus and had played a major role in its war with Israel in 2006.

The militant movement was infuriated by government allegations that it was spying on Lebanon's only airport, and by the cabinet's decision to remove from his post the head of airport security, a figure close to Hizbullah.

An unnamed Hizbullah source told Reuters protests would go on until the government rescinded these decisions, but government sources ruled out any U-turn.

Overnight, hundreds of Hizbullah members manned hastily assembled barricades and roadblocks and burnt tires in Beirut. The road leading to the airport remained closed today and Middle East Airlines, the national carrier, suspended all departures for 12 hours to "await positive developments".

Hizbullah has deemed the prime minister Fouad Siniora's cabinet illegitimate since its Shia members resigned in 2006 after he rejected their demands for veto power against government decisions. The crisis has paralysed much of the government and left Lebanon without a president for five months.

After the country's 16-year civil war ended in the early 1990s, Hizbullah was the only Lebanese faction allowed to keep its weapons to aid it in its efforts to drive Israeli forces out of south Lebanon. Israel eventually withdrew in 2000, and the fate of Hizbullah's weapons now is one of the key points of contention.

"Beirut relives the chapters of sectarian and militia horror," the pro-government An-Nahar newspaper said on its front page today. The opposition al-Akhbar newspaper said: "Lebanon in the mouth of the dragon."