One of Africa's most ambitious energy infrastructure projects has finally been signed off at the highest level, with West African leaders formally endorsing the long-awaited Nigeria-Morocco Atlantic Gas Pipeline.

"Don't be surprised when the gas comes your way," quipped Julius Maada Bio, Sierra Leone's president and the current head of West Africa regional bloc Ecowas, following Sunday evening's ceremony in Freetown.

The vast 6,000km (3,700 miles) pipeline will run along the Atlantic coast of 14 African nations, carrying Nigerian gas to Morocco before linking into Europe's existing gas network via Spain.

Construction is expected to begin in 2028 with a total estimated cost of $25bn (£19bn).

It signals a change from current models where gas is typically extracted from African nations, refined and processed abroad then shipped back to African nations at three or four times the price, says energy expert and former Nigerian government advisor Charles Majomi.

That practice must end, because it is a "complete devaluation of the resource that is so fortunately endowed in places like Nigeria and other countries," he told BBC Focus on Africa.

By contrast, if leveraged correctly, the new pipeline has the potential not just to stimulate regional industrial growth but also boost Africa's power on the international stage.

"In terms of Africa's regional security and its ability to negotiate and have a seat at the global table, if you will, it does need this measure of usefulness to countries [in] Europe and Asia potentially," argued Majomi.

"Beyond energy security, it will open up Africa as a corridor to international markets," Prof Ganiyat Adejoke Adesina-Uthman, of the National Open University of Nigeria, said.

It is a symbol of what Africa can achieve when countries collaborate and work together, she added.