BUJUMBURA, June 18 (Reuters) - Burundi's army said on Wednesday it had arrested more than 100 members of the country's last active rebel group, accusing the Hutu guerilla movement of breaking a truce by recruiting new fighters.

"The Forces for National Liberation (FNL) are trying to have as many fighters as possible, they are recruiting scores of new combatants, especially young people," said army spokesman colonel Adoplhe Manirakiza.

"This is of course a violation of the ceasefire agreement and we can't accept it."

The government and FNL signed a new peace agreement earlier this month after a 1996 one stalled on disputes over how to deal with demobilised fighters.

A final deal between the government and FNL is seen as crucial to lasting peace in Burundi, which is emerging from more than a decade of civil conflict that killed some 300,000 people.

The army said the 100 arrests were made on Tuesday and Wednesday in a rebel stronghold area 25 miles (40 km) south of the capital Bujumbura.

Rebel spokesman Pasteur Habimana said the detainees were not new recruits but combatants heading to assembly areas under the terms of a peace process.

"We urge their immediate release," he added.

The FNL gathered this week some 3,500 combatants in three different sites as a first phase before demobilisation and disarmament. It says it has 15,000 fighters.

(Reporting by Patrick Nduwimana; Editing by Matthew Tostevin)

(For full Reuters Africa coverage and to have your say on the top issues, visit:http://africa.reuters.com/)

(For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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