Colombia's FARC rebels begin a 30-day unilateral ceasefire Sunday as peace talks continue with the government to try to end Latin America's longest insurgency.

The Revolutionary Armed Forces of Colombia (FARC) asked its units to "cease fire and hostilities for 30 days" from December 15 in a message last week from Havana where the talks are being held.

President Juan Manuel Santos' government rejects the idea of any ceasefire until a peace deal has been signed.

Colombia has endured five decades of conflict that has left hundreds of thousands dead and displaced more than 4.5 million.

The FARC -- Colombia's largest and oldest rebel group, which was established in 1964 -- has 7,000 to 8,000 fighters.