Protests erupted across Lebanon on Monday as outgoing Prime Minister Saad Hariri's Western-backed party accused Hezbollah of staging a coup by imposing its candidate to head a new government.

Demonstrations were reported in various regions with a significant Sunni population where protesters burned tyres and blocked major roads as they vented their anger at the likely nomination of Najib Mikati to replace Hariri.

"Sunni blood is boiling!" and "Hezbollah, party of the devil!" chanted demonstrators in the northern port city of Tripoli, Mikati's home town and Lebanon's main Sunni bastion.

Former MP Mustafa Alloush, of Hariri's Future Movement, blasted the Iranian-backed Shiite militant group for staging a "coup" which he said was aimed at imposing an Iranian form of religious government in Lebanon.

Speaking at a news conference in Tripoli, Alloush called on the Lebanese to resist Hezbollah's attempt to "instate 'Velayat-e Faqih'," referring to Shiite Iran's form of Islamic rule.

He also called for a peaceful protest on Tuesday in Tripoli against Hezbollah.

Tripoli MP Mohammed Kabbara also called for a "day of anger" on Tuesday.

"This aggression against the Sunni confession and the nation is unacceptable," Kabbara said.

A security official told AFP that hundreds of demonstrators had cut off major roads leading in and out of the capital. Some demonstrators were seen overturning dumpsters and bringing in tyres to burn.

Roads were also cut off in the eastern Bekaa region, near the southern coastal city of Sidon and in several other towns in northern Lebanon.

The unrest came after Hezbollah and its allies put forward Mikati's name during consultations with President Michel Sleiman earlier on Monday.

Sleiman is due to announce his choice for the top post on Tuesday after meeting with all of the groups in parliament.

Hezbollah on January 12 brought down Hariri's Saudi- and Western-backed government after a long-running dispute over a UN-backed tribunal probing the 2005 murder of ex-premier Rafiq Hariri, Saad's father.

The militant party, blacklisted as a terrorist organisation by Washington, had been pressing Hariri to disavow the tribunal, which it believes will implicate Hezbollah members.

Hariri on Monday ruled out joining a government headed by a premier appointed by Hezbollah.