Colombia's former FARC Marxist rebel group has temporarily suspended its campaign for upcoming parliamentary elections due to security threats to its candidates.

FARC leader Pablo Catatumbo announced the party's decision on Friday in the capital, Bogota.

"We have decided to suspend campaign activity until we have sufficient guarantees. We call on all parties and political movements without exception, to make a statement rejecting this type of aggression," Catatumbo said during a press conference.

"We invite all to meet us at the forum to agree to a game of clean rules."

The FARC announced its decision after several of its candidates experienced verbal attacks at demonstrations and rallies.

The group shifted from being an armed rebel group to a political party, the Common Alternative Revolutionary Force party, last year, after it made a peace deal with the Colombian government in 2016. The group had fought a bloody 52-year campaign against Colombia's government before signing the peace agreement.

The agreement came after the group handed in more than 8,000 weapons and nearly 1.3 million pieces of ammunition as it demobilised, the United Nations said last year.

Many Colombians remain critical of the FARC and believe their leadership should be imprisoned.

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The FARC was formed in the early 1960s by fighters affiliated with Colombia's communist party intent on resolving long-standing issues such as land disputes and government neglect of rural areas, issues that still resonate in much of the nation today.

Over the next five decades, the conflict between the rebels, government forces and right-wing paramilitaries claimed at least 250,000 lives and left another 60,000 people missing. Millions more were displaced from their homes fleeing the bloodshed.