BRUSSELS (Reuters) - European Union governments approved a mission on Wednesday to help Libya improve its border security in response to concerns that Islamist militants and weapons move freely across the North African country's frontier.

The 110-member EU civilian team, expected to start deploying in Libya next month, will advise and train Libyan officials on how to strengthen the security of the country's land, sea and air borders, an EU statement said.

The EU team, being sent at Libya's request, will have a budget of 30 million euros ($39 million) for its first year and be based in Tripoli.

The Tripoli government has been beset by internal rifts and security remains a major concern long after a revolt and a NATO bombing campaign led to the death of Libyan leader Muammar Gaddafi in October 2011.

One of the triggers of the crisis in Mali in West Africa was the return from Libya of heavily armed fighters once in the pay of Gaddafi, regional security experts say.

These gunmen and the wide availability of arms during the Libyan conflict inflated the ranks of separatist and Islamist groups who launched attacks on Mali's army in early 2012.

Now, following France's military intervention in Mali, there is concern that militants are moving in the opposite direction.

Niger's foreign minister urged major powers in an interview with Reuters this month to act against Islamist militants who had found shelter in Libya's vast southern desert and, he said, posed a growing threat to neighboring countries.

Mohamed Bazoum said Niger had information that Islamists who had been driven out of northern Mali were setting up bases in Libya's lawless south, which borders Niger.

The Libyan government has also said it is worried about an influx of al Qaeda-linked fighters from Mali.

(Reporting by Adrian Croft)