Tripoli, Lebanon ? Lebanese army tanks pounded a shadowy group suspected of ties to al-Qaida on Sunday, targeting its hideouts inside a Palestinian refugee camp after hours of clashes killed at least 22 soldiers and 17 militants.

A Lebanese soldier carries an RPG launcher Sunday as he sits behind a wall during a clashes with Islamic militants on a street in the north city of Tripoli. Lebanese security forces fought Islamic militants in the northern city of Tripoli and an adjacent Palestinian refugee camp early Sunday. Seven members of the security forces were killed and 29 people wounded in fighting that involved tank and grenade fire, security officials and rescuers said.

The violence between the army and the Fatah Islam group erupted both in the northern port city of Tripoli and the adjacent Nahr el-Bared refugee camp. It added further instability to a country already mired in its worst political crisis between the Western-backed government and Hezbollah-led opposition since the end of the 1975-90 Lebanese civil war.

It was the most serious fight the army had engaged in Lebanon in more than a decade and the worst violence to hit Tripoli in two decades.

The clashes between army troops surrounding the camp and Fatah Islam fighters began after a gunbattle raged in a neighborhood in Tripoli, a predominantly Sunni city known to have Islamic fundamentalists, witnesses said.

Fighting spread after police raided suspected Fatah Islam hideouts in several buildings in Tripoli, searching for men wanted in a recent bank robbery. A gunbattle ensued and troops were called in to help the police.

Militants then burst out of the refugee camp, seizing Lebanese army positions, capturing two armored vehicles and ambushing troops. They killed two soldiers on roads leading to the city.

Smoke billowed from the camp as a steady barrage of artillery and heavy machine gunfire from army positions pounded militant positions inside.

Security forces were able to quell the resistance in Tripoli after sundown, and troops seized all positions around the refugee camp late Sunday, the army said.

In Beirut late Sunday, an explosion across the street from a busy shopping mall killed a 63-year-old woman and injured 12 other people in the Christian sector of the Lebanese capital, police said.

A wall in the woman’s nearby apartment collapsed on her from the impact of the blast, said the Lebanese Broadcasting Corp., a Christian TV station.

The bomb left a crater about 4 feet deep and 9 feet wide, and police said the explosives were estimated to weigh 22 pounds. The blast – heard across the city – gutted cars, set vehicles ablaze and shattered store and apartment windows.

Beirut and surrounding suburbs have seen a series of explosions in the last two years, many targeting Christian areas. Authorities blamed Fatah Islam for Feb. 13 bombings of commuter buses that killed three people, but the group denied involvement.

Cabinet minister Pierre Pharaon said Sunday’s explosion was aimed at undermining Lebanon’s security as the U.N. Security Council considers imposing an international tribunal to try suspects in the assassination of former Premier Rafik Hariri.

A U.N. investigation has linked Syrian and Lebanese security officials to the 2005 truck bombing that killed Hariri, and it has been expanded to include the other Beirut attacks.

Syria has denied involvement in any of the bombings, but the country was forced to withdraw its army from Lebanon after a 29-year presence two months after Hariri’s assassination.

Hundreds of Lebanese applauded the army’s tough response in the refugee camp in a sign of the long-standing tensions that remain between some Lebanese and the estimated 350,000 Palestinians who have taken refuge in Lebanon since the creation of Israel in 1948.