ABU DHABI (AFP) - A total of 750 French troops have joined the offensive against Islamist rebels in Mali where overnight strikes "achieved their goal," French President Francois Hollande said in Abu Dhabi on Tuesday.

"For now, we have 750 men and the number will increase ... so that as soon as possible we can leave the place to the African forces," said Mr Hollande during a visit to Peace Camp in Abu Dhabi, his country's only military base in the region.

"France will continue to have ground and air forces," he said, adding that deployment of African forces in Mali "will take at least a week."

"New strikes overnight achieved their goal," he told reporters while touring the base.

French forces have, since Friday, been supporting an offensive by Malian government troops against Islamist groups which have controlled the north of the vast country since April 2012.

The military intervention has driven Islamists fighters from their strongholds in the north but the rebels on Monday pushed farther into the government-held south, seizing the town of Diabali, 400 km north of the capital.

Mr Hollande flew into the oil-rich United Arab Emirates where soon after his arrival on Tuesday held talks with Mauritanian President Mohamed Ould Abdel Aziz in Abu Dhabi.

Mauritania, Mali's western neighbour, ordered its troops to seal the border to prevent Islamists fighters from escaping into their territory.

Mr Hollande will hold meetings with the rulers and senior officials from both Dubai and Abu Dhabi during his one-day visit.

On the presidential plane that left Paris on Monday, Mr Hollande's entourage said that some 700 soldiers in the French base in Abu Dhabi, along with six Rafale jets stationed there, were on alert if needed to participate in the Mali offensive.

"Mali is still not in our field of action for now ... (but) if we receive orders, we will implement them," said an official at the base.