Suspected drug planes that enter Guinea-Bissau's airspace will be shot down in a bid to reduce rampant cocaine trafficking, the government says.
Guinea-Bissau is one of the major drug transit hubs in West Africa
Prime Minister Martinho N'Dafa Cabi said he had personally issued the uncompromising order.
This follows the army's seizure of a truckload of jet fuel in a forest outside the city of Buba on Thursday.
International drugs experts fear the poor, unstable country with numerous islands could become a "narco-state".
Mr N'Dafa Cabi said the order was "a means of threatening" drug traffickers "who profit from our fragility".
While the army chief of staff, General Tagme Na Waye said anti-aircraft guns were "already installed" on all the Bijagos Islands, and, "any plane detected in this zone without authorization will be shot down."
West Africa has fast become a transit hub for South American cocaine on its way to Europe - often via its many uninhabited islands, which are large enough for an airstrip.
The fuel found near Buba was enough to fill a mid-sized Gulfstream jet tank twice.
Interpol estimates that more than a third of the cocaine arriving in Europe is trafficked through West Africa.
The government of Guinea Bissau is telling the world that it intends to end the drug trafficking, but BBC West Africa correspondent Will Ross says it is clear that the very people who should be countering it have been involved.
Earlier this year a consignment of over 2.5 tonnes of cocaine was flown into a military airstrip.
Two soldiers were later arrested in cars which had been packed with over 600kg of cocaine.
Last year around $40m worth of cocaine was found in the capital, Bissau, after a gun battle.
It was stored in the treasury vaults but was never seen again, and nobody has been able to prove the claim that it was burnt.
After years of instability, the country is in ruins and does not even have a proper prison.