African leaders gathered in Togo's capital Lome on Saturday to tackle rising piracy and smuggling off the continent's coasts, twin scourges holding back economic development.

Chad's head of state Idriss Deby, the current African Union president, opened the summit, noting that some 90 percent of Africa's imports and exports were transported by sea, making maritime security key to the continent's economic future.

More than 40 countries have sent representatives to the AU's "Protect Our Oceans" meeting hoping to sign a new charter on maritime security.

The leaders include 18 heads of state -- an unusually high figure for an AU meeting of this kind -- signalling the importance that governments place on the need to cut piracy and other crime in Africa's waters.

Of the AU's 54 member states, 43 have coastlines.

Deby said the charter would "allow the promotion of commerce and the exploitation of the huge potential of the maritime sector, as well as the creation of wealth and jobs in several industries".

It would also "mark a decisive new step in the push to preserve the maritime environment", he added.

- Hijackings -

Piracy, smuggling and other crimes at sea have cost the African maritime sector hundreds of billions of dollars in recent decades, according to the AU.

"Most African countries that have a coastline are victims of one of these problems, which is why it's so important for African leaders to sit down and try to find solutions," Togo's Foreign Minister Robert Dussey told AFP ahead of the summit.

World piracy has been on the decline since 2012 after international naval patrols were launched off East Africa in response to violent attacks by mostly Somali-based pirates.

But the focus of concern has shifted to the Gulf of Guinea, particularly the waters off oil-rich Nigeria.

The perpetrators are often offshoots of militant groups from the Niger Delta seeking a fairer distribution of the revenues from the continent's largest oil reserves.

At least 27 attempted or successful hijackings and kidnappings at sea have been recorded off west Africa since April, according to the International Maritime Organization, compared to just two off east Africa.

The 17 countries lining the Gulf of Guinea have poor maritime surveillance capacities and they have been trying for several years to boost cooperation to clamp down on piracy.

Regional coordination centres have been mooted, but progress has been slow and there have been few offers to fund the project. The binding charter that leaders are hoping to sign Saturday would create a funding mechanism for the initiative.

"Africa is more exposed than the other continents for the simple reason that it has less expertise and fewer means to face the situation," Deby said ahead of the summit on Friday.

Large-scale illegal fishing also helps drive piracy as it depletes stocks, reducing the legitimate economic activities of coastal communities.

In West Africa alone, the AU estimates that illicit fishing causes losses of 170 billion CFA francs ($285 million, 260 million euros) every year.

One project on the table to reduce these losses is a catch certification scheme for the import and export of fishery products.