A Lebanese soldier runs past burning tires lit by Sunni Muslim supporters of Lebanon's caretaker prime minister Saad Hariri during what they called a day of rage in Sidon, southern Lebanon. (Ali Hashisho/Reuters)

Thousands of angry Sunnis took to the streets of Lebanon on Tuesday to protest the nomination of Hezbollah-backed candidate Najib Mikati as the next prime minister.

Mikati, a billionaire businessman and former premier, was appointed prime minister-designate after a majority of legislators voted for him in the morning.

He defeated Saad Hariri, prime minister from 2009 until Hezbollah forced the unity government he led to collapse two weeks ago.

Lebanese prime minister-designate Najib Mikati says his hand is 'extended to all Lebanese, Muslims and Christians, in order to build and not to destroy.' (Sharif Karim/Reuters)

His election, which had been widely anticipated, sparked massive demonstrations in the northern city of Tripoli, in the capital of Beirut, and the southern port city of Sidon, as well as the highway between Beirut and Sidon.

The largest gathering was in the northern city of Tripoli, a predominantly Sunni area and a hotbed of fundamentalists where thousands of people converged at a major square.

Protesters burned tires and waved flags, shouting their support for Hariri. Some protesters also attacked a truck belonging to Al-Jazeera television and set it on fire.

After meeting with President Michel Suleiman near Beirut, Mikati called for another unity government.

"My hand is extended to all Lebanese, Muslims and Christians, in order to build and not to destroy," Mikati said after he was chosen, striking a conciliatory tone.

Suleiman will now ask Mikati to try to form a new government that could be controlled by Hezbollah and its allies, and give the group an unprecedented level of political power in Lebanon.

The vote caps Hezbollah's steady rise over the past few decades from a resistance group fighting Israel to Lebanon's most powerful military and political force.

Many fear international isolation if Hezbollah pushes its power too far.

Hezbollah's Sunni opponents maintain that having an Iranian proxy in control of Lebanon's government would be disastrous and lead to international isolation.

Hariri thanked people for their support, but called for restraint.

"I understand your emotions … but this rage should not lead us to what is against our morals, faith and beliefs," he said.

Hariri refuses Hezbollah-backed government

Mikati urged calm Tuesday and said he wanted to represent all of Lebanon.

Sunni supporters of Lebanon's caretaker prime minister Saad Hariri took to the streets in Sidon, in southern Lebanon, on Tuesday. (Ali Hashisho/Reuters)

"This is a democratic process," Mikati told reporters. "I want to rescue my country."

Hezbollah brought down Hariri's Western-backed government on Jan. 12, when he refused to obey their demand that he cease co-operation with a UN-backed tribunal investigating the 2005 assassination of his father, former prime minister Rafik Hariri.

Hezbollah, which denies any role in the killing, is widely expected to be indicted.

The group can now either form its own government, leaving Hariri and his allies to become the opposition, or can try to persuade Hariri to join a national unity government.

Hariri said Monday he will not join a government headed by a Hezbollah-backed candidate.

Hariri's Future bloc declared a day of peaceful protests Tuesday, but called it a "day of rage" and played on the sectarian dimension of the conflict.

With files from The Associated Press