The Lebanese army has resumed shelling a besieged Palestinian refugee camp, a day after it said important militant positions had been destroyed.

Troops targeted suspected hideouts of the Fatah al-Islam group, as fighting entered a fifth week in Nahr al-Bared.

Shelling sent thick plumes of smoke into the air and started fires.

More than 150 people have been killed, including at least 20 civilians, in the worst internal violence in Lebanon since the end of the 1975-90 civil war.

The government is currently tackling militants on two fronts, after gunmen on Sunday fired rockets into Israel from southern Lebanon.

Lebanese troops and UN peacekeepers were put on full alert as they increased patrols in border areas.

It was the first time rockets were fired into Israel since year's devastating war between the Israeli army and the Lebanese Shia group Hezbollah.

Israel blamed the rocket fire - which caused material damage but no casualties - on an unnamed Palestinian organization. Hezbollah denied responsibility.

Flags flying

On Sunday the Lebanese army said it had destroyed the Fatah al-Islam headquarters and another building on the edge of the camp, situated north of the northern Lebanese city of Tripoli.

Militants had used the buildings to fire on Lebanese troops besieging the camp.

Reports said Lebanese flags were flying over the two buildings on Monday.

The army said it had now pushed the militants back into the southern sector of the impoverished refugee camp, which houses Palestinians who fled their homes when Israel was created in 1948.

Approximately 2,000 refugees are believed to remain inside the camp, which was home to 31,000 people.

PHOTO CAPTION

Tank fire at Nahr al-Bared refugee camp