Two people have been killed in northern Lebanon in fighting between supporters and opponents of the Syrian government and the Lebanese army, which is struggling to curb violence stemming from the neighbouring country's civil war.
The incident on Monday is the latest in a series of clashes that broke out last Tuesday and continued over the weekend, in which 17 people have been killed and more than 100 wounded.
Security forces will take every step to put an end to the violence and chaos.
The fighting has been concentrated in the Bab al-Tebbaneh and Jabal Mohsen districts of Tripoli, Lebanon's second largest city, where Sunni Muslims and Shias from Syrian President Bashar al-Assad's Alawite sect have clashed on and off for decades.
The Lebanese army was deployed to Tripoli on Monday. The Syrian conflict has reopened old wounds, with each side accusing the other of using the city as a base for sending fighters and weapons in and out of Syria.
Tanks and jeeps entered the northern sector of Bab al-Tebbaneh but their progress was slowed by sniper fire to which the troops responded, according to a reporter of the AFP news agency.
A security official said the army has also been deployed in Jabal Mohsen, which adjoins Bab al-Tebbaneh.
Residents of Bab al-Tebbaneh support the revolt against Assad, while those in Jabal Mohsen back the Syrian president. They have fought frequently since the Syrian conflict erupted in March 2011.
Lebanon is deeply divided into pro- and anti-Damascus camps. Lebanese Shia movement Hezbollah has sent fighters into Syria to support Assad's troops, while Sunni organisations have sent men across the border to fight alongside rebels.
Tripoli is home to 200,000 people, 80 percent of whom are Sunni Muslims, 6-7 percent Alawites and the rest Christians.
Acting Prime Minister Najib Mikati said on Saturday that "security forces will take every step to put an end to the violence and chaos" in the city. "They will be strict and impartial."
But residents of Syria Street, which separates the mostly anti-Damascus Bab al-Tebbaneh and the pro-Assad Jabal Mohsen, were sceptical.
"This is all a joke. It is the eighteenth time since May, 2008 that they come to help. In fact, the army makes a small tour and then leaves. There is no solution," said Mustapha al-Hajj, a 69-year-old retired man
"In the past eight days, 400 families have left Syria Street, including my own. We sleep under the stars, me, my wife and our three children, in a park in the city."
"Each month it's the same thing," al-Hajj added.