BRUSSELS, Sept 29, 2008 (AFP) - The European Union military force in Chad and the Central African Republic will strive to ensure that no security vacuum develops as a UN force takes over next year, the EU commander vowed Monday.

'Our aim is not to let any security gap develop,' said Lieutenant General Patrick Nash, the Irish head of the so-called EUFOR peacekeeping mission, whose mandate runs out in mid-March.

'Many challenges remain: we do not underestimate the fragility and instability of the security situation,' he said, but he underlined that 'there now exists a greater sense of security' in the area.

In eastern Chad, carjackings, armed robberies and crime targeting national and international humanitarian staff continue, impeding their efforts to help nearly 300,000 refugees and almost 200,000 internally displaced persons (IDPs).

In March, EUFOR began a year-long UN mission to protect refugees from western Sudan's strife-torn Darfur region as well as people displaced by the rebel insurgency in Chad and the northern Central African Republic (CAR).

Last Wednesday, the UN Security Council unanimously approved a resolution extending until March 15, 2009, the mandate of the UN mission in the Central African Republic and Chad (MINURCAT).

The French-sponsored resolution also said the 15-member Council planned to authorize the deployment of a UN military component to follow up EUFOR in Chad and CAR, as recommended by UN chief Ban Ki-moon.

'My mandate is to be operational until the 15th of March and then to recover the forces,' Nash told reporters in Brussels. He expected 'to have all troops out of Chad before the 1st of June,' he added.

He also said that four transport helicopters promised to the mission by Russia were expected to be in operation by the beginning of November.

EU defence ministers are due to discuss the mission and the transition to the United Nations at informal talks in Deauville, northern France, starting Wednesday.