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By Nadim Ladki

BEIRUT, May 7 (Reuters) - Demonstrators blocked several roads in and around Beirut with burning tyres on Wednesday as part of an anti-government protest backed by Lebanon's Hezbollah-led opposition, witnesses said.

The main road leading to the capital's international airport was among routes blocked by the protesters.

In Lebanon's worst political crisis since its 1975-1990 civil war, Hezbollah has been leading a campaign against Prime Minister Fouad Siniora's government since November 2006. The standoff has left Lebanon without a president for five months.

The Syrian-backed opposition had urged supporters to back a strike by Lebanon's main labour union, which is demanding higher wages.

Security forces were deployed ahead of a march called by union leaders for later on Wednesday.

On Tuesday, the Western-backed government accused Hezbollah, a political group with a guerrilla army, of violating Lebanon's sovereignty by operating its own communications network and installing spy cameras at Beirut airport.

The government, supported by the United States and a number of Arab countries including Saudi Arabia, also removed the head of Beirut airport security in another challenge to Hezbollah, which is backed by Iran and Syria.

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

It was the only Lebanese faction allowed to keep its weapons after the civil war to fight Israeli forces occupying the south. Israel withdrew in 2000 and the fate of Hezbollah's weapons is at the heart of the political crisis. (Editing by Ralph Gowling)

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