The food crisis in Africa's Sahel region is "deepening", Christian Aid has warned.

The development agency said thousands of people along the border with Niger and Burkina Faso were being forced to leave their homes in search of food.

One of the worst affected areas is north Burkina Faso, where Christian Aid has sent a task force to oversee an emergency feeding programme.

The crisis has been triggered by a combination of failed rains and widespread drought.

According to the aid agency, Mali lost 11.8% of total cereal output between 2010 and 2011. In Burkina Faso, it is estimated that 41.47% of the country will face severe food insecurity.

The Niger government believes that more than half of the nation’s villages are now running out of basic food.

Many families in the Sahel are buoyed by money sent to them from relatives working in Libya and the Cote d'Ivoire. Recent conflicts in both countries have hit them hard as the work situations have become less stable, meaning relatives may have had to send home less or halt transfers altogether.

A joint evaluation of the region last month by major bodies including the World Food Programme estimated that nearly 5.5 million people in Niger are "food insecure". This includes 1.3 million at levels deemed "severe".

In Mauritania, 700,000 people - more than a quarter of the population - are food insecure, and in Burkina Faso, 1.7 million people are "vulnerable".

Evaluations are underway in Mali, Chad and Senegal but numbers are expected to be similar.

The World Food Programme and Farming and Agriculture Organisation estimate that three million people in Mali and 850,000 people in Senegal live in areas at risk.

The European Commission estimates that at least 7 million people in the entire region will need support over the next six months.