Sept 2 (Reuters) - Lebanese troops took control on Sunday of a Palestinian refugee camp where they had been battling militants for more than three months, killing at least 31 fighters who tried to flee, security sources said.

Thirty-four more fighters from the Fatah al-Islam group were captured, 23 of them inside the Nahr al-Bared camp in north Lebanon. The violence is Lebanon's worst internal fighting since the 1975-1990 civil war.

The battle has added to instability in Lebanon. Here is a chronology of the country's recent problems:

August 1990 - Parliament enacts Taif Accord, which becomes Lebanon's new constitution, bringing an end to civil war which killed some 150,000 people since it erupted in 1975.

October 1992 - Lebanon holds first postwar elections. Rafik al-Hariri becomes prime minister.

May 2000 - Israel ends 22-year occupation of south Lebanon.

October 2000 - Hariri chosen prime minister again after popular discontent with economic slide.

June 2001 - Syria completes surprise pullout of its troops from Beirut and surrounding areas.

February 2005 - Former prime minister Hariri is killed by a bomb in Beirut. Two months later, under international pressure, Syria ends its 29-year military presence in Lebanon.

July 2006 - Israel strikes Lebanon after Hezbollah guerrillas abduct Israeli soldiers. At least 1,200 people die in Lebanon in 34 days of fighting.

November 2006 - Industry Minister Pierre Gemayel is killed by gunmen as his convoy drives through the Christian Sin el-Fil neighbourhood of Beirut.

All Shi'ite ministers resign from Lebanon's cabinet, skewing the sectarian balance in Lebanon's power-sharing system.

December 2006 - The opposition, which also includes the Shi'ite Amal faction and Christian leader Michel Aoun, begins an open-ended campaign in central Beirut to topple the government.

January 2007 - A general strike is called by the Hezbollah-led opposition to dislodge Prime Minister Fouad Siniora and his pro-Western government. Supporters of rival factions clash in the worst civil strife since the war.

March 2007 - Rivals anti-Syrian majority leader Saad al-Hariri, a Sunni Muslim, and Shi'ite Parliament Speaker Nabih Berri, a key opposition leader, meet for the first time in four months to discuss ways to end the political crisis.

May 20-21 - Fighting erupts in north Lebanon between the Lebanese army and Sunni Islamist militants of the Fatah al-Islam group. Thousands of Palestinian refugees are forced to flee the Nahr al-Bared camp where the militants are based.

June 13 - Anti-Syrian legislator Walid Eido and nine other people are killed by a car bomb in Beirut. The capital and its suburbs are also gripped by tension because of a series of smaller bombings, the first of which was on May 20.

June 25 - A car bomb driven by a suicide bomber kills six U.N. peacekeepers in south Lebanon.

Sept 2 - Lebanese troops seize complete control of Nahr al-Bared camp after more than three months of fighting which kills over 300 people. The battle is Lebanon's worst internal violence since the civil war.

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