Trafficking is fuelling addiction as well as terrorism
The head of the UN drugs agency (UNODC) has warned that widespread drug trafficking is transforming Africa into a major crime hub.
Antonio Maria Costa said huge amounts of heroin and cocaine were being traded by "terrorists and anti-government forces" to fund their operations.
He called for a trans-Saharan network to be set up to tackle criminal groups.
Last month the wreckage of a Boeing 727 was found in Mali with up to 10 tonnes of cocaine from Venezuela on board.
"It is scary that this new example of the links between drugs, crime and terrorism was discovered by chance," Mr Costa told the UN Security Council.
He said 50 to 60 tonnes of cocaine were trafficked every year across West Africa while another 30 to 35 tonnes of Afghan heroin was being trafficked into East Africa every year.
He said the drug streams were crossing in the Sahel - an arid area extending across northern Africa, just south of the Sahara, where militant groups such as the north African branch of al-Qaeda operate.
Drug-trade expert, University of Wisconsin
Just four years ago the deputy director of the UNODC said that with the exception of Nigerian trafficking and khat - the local drug in East Africa - Africa was a continent that was really effectively insulated from the global drugs traffic. The UN felt the international community had Africa under control.
If Mr Costa is correct - and he usually is on these points - the last of the five inhabited continents of the globe has now succumbed to drug trafficking.
This is because a boom in production has saturated global markets. In the last 10 years the world supply of opium and heroin has doubled from 4,000 to 8,000 tonnes.
Drug traffickers have saturated Russia, much of Western Europe, and they are now spreading into Africa.
"Drugs not only enrich organised crime... terrorists and anti-government forces in the Sahel extract resources from the drug trade to fund their operations, purchase equipment and pay foot-soldiers," he said.
He said the flow of drugs through East Africa was being facilitated by Somalia's collapse, and in West Africa Guinea-Bissau was becoming a trafficking hub.
He also warned that the continent was seeing "a dramatic increase in drug addiction", which was helping to spread Aids.
Mr Costa called for African countries to share information more effectively and create a trans-Saharan crime monitoring network.
Alfred McCoy, an expert in the international drug trade, told the BBC's World Today programme such an approach was unlikely to work.
"One has to be pessimistic about the capacity of enforcement to contain a global commodity," he said.
"The problem is not the traffickers or the traffic, the problem is the whole drug war - we're brining the blunt baton of repression down on a global commodity and the results have generally been negative."
For his part, UN Secretary-General Ban Ki-moon said drug trafficking was also affecting peacekeeping efforts in Afghanistan, Haiti, Guinea-Bissau and elsewhere.
"So far, co-operation between governments is lagging behind co-operation between organised crime networks," Mr Ban said.
The UN Security Council adopted a statement voicing concern about the impact of the African narcotics trade and calling for stronger regional co-operation in the fight against illegal drugs.