West African leaders have signed an agreement approving the construction of a gas pipeline linking Nigeria to Morocco at a summit of regional bloc ECOWAS in Sierra Leone's capital Freetown.

The pipeline is designed to transport up to 30 billion cubic ​metres (bcm) of natural gas a year from Nigeria ​and west Africa through 13 West African countries ⁠to Morocco, according to a joint statement by ​Morocco’s hydrocarbons and mining agency ONHYM and Nigeria's state ​oil firm NNPC.

Of that capacity, 15 bcm a year will be made available to Moroccan and European markets through an existing ​pipeline that links Morocco to Spain, the statement said.

The next phase includes creating a "project company" based in Casablanca and a governing authority headquartered in Abuja before investors are brought on board and a final investment decision is taken.

Construction is expected to begin in 2028, with the first gas deliveries targeted for 2031, according to sources.

The project, first proposed during Moroccan King Mohammed VI's visit to Abuja in 2016, is estimated to cost around $27 billion.