Lebanese army forces and Sunni Islamist militants, thought to be linked to Islamic State, have been involved in intense fighting in the country's second city, Tripoli.

The army says it has surrounded dozens of militants in the city's old market district.

Clashes between opponents and supporters of the Syrian President Bashar al-Assad have regularly erupted in Tripoli, but have rarely spread beyond one neighbourhood where tensions are highest.

Jim Muir reports from Beirut.