Thousands of West African nationals are being deported from Nigeria in an exercise by the government to clear the country of illegal aliens.Authorities say the illegal aliens constitute a “public nuisance and security risk.”Citizens from Niger and Chad seem to have been the most affected by the exercise although citizens from other West African countries such as Ghana, Togo and Cameroon are also said to be affected by the exercise.The BBC’s correspondent in Nigeria, Manir Dan-Ali told Joy News that although official reasons indicate that the exercise is an annual affair, some people say the current one is in connection with the country’s national polls scheduled for April.The Nigerian High Commission in Accra said it was yet to be briefed on the scope of the exercise and who was being targeted.Officials however maintained that the exercise was a yearly ritual that sees a number of foreigners with improper documentation returned to their countries.