The haul arrived by sea and was hidden in flour bags - the second big shipment to be seized this year, the Reuters news agency reports.

According to Guinea-Bissau's privately owned O Democrata news agency, those arrested were three Colombians, one Malian and four Guinea-Bissau nationals.

"The drugs belong to the terrorist network al-Qaeda. The cocaine comes from Colombia. But the destination is the Arab Maghreb,” Reuters quoted Domingos Monteiro, a top police commander, as saying.

Al-Qaeda in the Islamic Maghreb (AQIM), is one of the best-armed Islamist militant groups in North Africa thanks to the money it makes from drug and cigarette trafficking across the Sahara and the kidnapping of Westerners.

Guinea-Bissau has been a staging post for gangs smuggling cocaine from Latin America to Europe.

The small West African state has been described by the UN as a "narco state", but following the arrest of some top officials by the US authorities in 2012 cocaine traffic in the country seemed to decline or go underground, Reuters reports.