A similar clash erupted last week in Tripoli after Lebanese troops stormed a hideout, killing seven, mostly foreigners.
A more significant clash erupted on May 20 in Tripoli which lead to fierce fighting at a nearby Palestinian refugee camp between the army and Fatah al-Islam fighters.
The fighting since then has killed at least 194 people - 84 soldiers, 70 fighters and 40 civilians - not including Thursday's casualties.