The authorities in Burkina Faso say four army officers have been detained for questioning a day after the military government announced it had thwarted a coup attempt.

The military prosecutor's office also said two officers were on the run.

It is almost a year since Captain Ibrahim Traoré seized power - the second coup in the country in eight months.

But there have been signs of tension within the military.

The military prosecutor says an investigation has begun and has appealed for witnesses following what he called attempts at destabilizing the country.

Even before the announcement that a coup plot had been foiled there were signs that all was not well within the armed forces.

Three weeks ago there was another move against the ruling junta.

In Burkina Faso, Mali and Niger military men used a deteriorating security situation as justification for seizing power.

Thousands of UN troops and French soldiers are leaving the region after being ordered out.

There is a danger that Islamist militants are going to take advantage of all these changes and the insecurity in the Sahel will get even worse.