May 21 (Reuters) - Lebanese tanks shelled Islamist militants in a Palestinian refugee camp on Monday and at least nine civilians were killed, raising the death toll in two days of fighting to more than 70, security sources said.

Here are some key facts about Lebanon.

THE COUNTRY:

POPULATION: 4.2 million.

AREA: 10,452 square km (4,036 square miles). It is bordered to the south by Israel and to the north and east by Syria.

CAPITAL: Beirut. Population around 1.5 million.

RELIGION: Muslims make up around 65 percent of the population, just over half of whom are Shi'ites. There is a large Christian population, predominantly Catholic and Maronite but also Orthodox. There is a sizeable Druze minority.

PALESTINIAN REFUGEES: The United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) says there are 12 official camps in Lebanon for Palestinian refugees -- part of an exodus prompted by the 1948 war that followed Israel's creation. Palestinian refugee camps in Lebanon all suffer from overcrowding, poverty and unemployment. The number of Palestinian refugees registered with UNRWA in Lebanon is 394,532, around 10 percent of Lebanon's population. UNRWA says the majority rely on it as the sole provider of social services.

RECENT CHRONOLOGY:

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 the 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.

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 - Lebanese troops battle al Qaeda-linked militants, members of the Fatah al-Islam militant group, in northern Lebanon and at least 71 people are killed, 27 of them soldiers, after security forces raid homes in Tripoli to arrest suspects accused of robbing a bank a day earlier.

WHAT IS AT STAKE:

* Security is already fragile in Lebanon, hit by a series of assassinations and bombings since the 2005 killing of former Prime Minister Rafik al-Hariri. The clashes in the north have further stretched the army, already strained by its deployment last year in south Lebanon.

* The army has also been stretched by policing demonstrations during Lebanon's current political crisis -- the worst since the 1975-1990 civil war. Ten people have died in violence related to the crisis. Siniora has accused Hezbollah of trying to stage a coup and commentators and politicians have warned that the worsening stand-off could degenerate into sectarian violence.

* The political crisis has hit the economy hard and hindered the government's ability to implement economic reforms agreed with international donors at a conference in Paris in January. The reforms are required for Lebanon to secure the billions of dollars pledged. Much of the money is to help ease Beirut's massive public debt mountain.

* Further instability is likely to wreck the summer tourism season, further damaging the economy.

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