Cuba's President Raul Castro (C) stands as Colombia's President Juan Manuel Santos (L) and FARC rebel leader Rodrigo Londono, better known by the nom de guerre Timochenko, shake hands in Havana, September 23, 2015. [Photo/Agencies]

HAVANA - Colombian President Juan Manuel Santos and the leader of the FARC Rodrigo Londo?o Echeverri, also known as Timoleon Jimenez, announced in Havana Wednesday that the two sides had reached a landmark understanding about how to bring their long civil war to an end.

The two sides signed an agreement that lays out guidelines regarding how Colombia will investigate human rights abuses and punish the guerrillas held responsible for those abuses and how to compensate victims, according to a press conference held Wednesday afternoon.

While addressing Echeverri who was seated at his side, Santos praised "the steps the FARC has taken today. We are adversaries but we now advance in the same direction...which is toward peace".

According to Santos, Colombian government and the guerrilla rebel group -- the Revolutionary Armed Forces of Colombia (FARC) -- also agreed to seal a final peace agreement within six months, specifically by March 23, 2016, bringing an end to the peace talks of more than three years in Havana, the Cuban capital.

However, obstacles remain as both sides must still work on and agree to how guerrillas will be demobilized and disarmed, said the Colombian president.

The two sides will create specific bodies to oversee parts of the peace process, including a special commission tasked with matters related to reparations paid out to victims and a dedicated tribunal set up to extend amnesty to combatants except those who committed war crimes.

Santos promised the peace deal, which is expected to end the 51-year-long war in Colombia, will be voted on by the Colombian people in a national referendum.

While the announcement of Wednesday's agreement was heralded widely by the international community, Alvaro Uribe, predecessor of Santos, lambasted the deal on his Twitter account, saying "It's not peace that's near, it's surrender to the FARC."