Kigali - Forty-four African countries have signed an agreement establishing a free trade area seen as vital to the continent's economic development, the head of the African Union said Wednesday.

"The agreement establishing the CFTA (African Continental Free Trade Area) was signed by 44 countries," said Moussa Faki Mahamat, chairperson of the AU commission.

The creation of a free trade area - billed as the world's largest - comes after two years of negotiations, and is one of the AU's flagship projects for greater African integration.

However, the agreement will still have to be ratified at a national level, and is only due to come into force in 180 days.

The full list of countries which did not sign the agreement is not yet available, however Nigeria is a notable absentee after President Muhammadu Buhari pulled out of this week's launch in Rwanda saying he needed more time for consultations at home.