Colombia's former FARC rebel group has relaunched as a political party, changing their logo of rifles for a red rose after disarming to end a half-century civil conflict.

"We want to build a new country together with you," FARC commander Rodrigo Londono told a rally of thousands of supporters in the capital Bogota on Friday.

"A nation in which no one is persecuted or killed for thinking differently," he continued.

The new party will have a "broad character, a new party for a new Colombia", the group's former military commander Pablo Catatumbo said at a press conference.

It will be a movement "committed to guarantee social justice, peace, sovereignty and agrarian reform, for the defence of popular interests", he said.

On Thursday, Londono announced the name of the new party: The Common Alternative Revolutionary Force.

The name controversially retains the same acronym (FARC) and the revolutionary spirit of the Marxist rebel group, which fought a bloody 52-year campaign against Colombia's government before signing a peace deal last year.

Demobilised and renamed, the party now faces a struggle for political acceptance in a country scarred by decades of attacks and kidnappings.

Al Jazeera's Alessandro Rampietti, reporting from Bogota, said the group, as a political party, will be fighting an "uphill battle".

"At least 70 percent of the country has said they will never vote for them," he said. "At the same time, however, their favourability has been going up."

'Revolutionary' force

FARC delegates spent the week in a founding congress to choose their political representatives and its new name.

Some FARC leaders wanted to keep the "revolutionary" element, while others wanted to soften the group's image by dropping it in favour of "New Colombia".

In the end, a majority voted to call it in Spanish Fuerza Alternativa Revolucionaria del Comun, meaning it will still be known as the FARC for short.

The logo for the new party is a socialist-style red rose with a star in its centre above the letters FARC in green.

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The former armed group's logo was two crossed rifles under a book.

The FARC formed as a communist movement in 1964 from a peasant uprising for rural land rights.

Over the following decades, the conflict drew in various rebel forces, paramilitary groups and state forces.

It left some 250,000 people confirmed dead, 60,000 unaccounted for and seven million displaced in Latin America's longest conflict.

The new party will compete in next year's general elections.

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Catatumbo told AFP news agency that the new party plans to formally select its new political representatives by November. Among them are likely to be several former prominent commanders, including Catatumbo himself.

Regardless of how many votes they may win, the peace deal signed with the government last year guarantees the FARC five seats in each of the two legislative chambers for two terms.

Demobilisation

Colombians narrowly rejected the government's peace deal with the FARC in a referendum last year.

President Juan Manuel Santos and the FARC then tweaked it and the government pushed it through Congress.

As part of the deal, 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 month.

Roughly 7,000 FARC fighters have demobilised under the accord, which grants amnesty to the majority of ex-fighters.

"We have entered legal political life because we want to be a government or be part of it," said Ivan Marquez, the rebels' chief negotiator in the talks with Santos's government.

The new FARC will seek to build "a large democratic coalition of broad convergence, built on shared policies and mutual commitments".