The United States military is expanding a secret network of air bases across Africa in order to spy on al-Qaeda and other such groups, a US newspaper said.

The surveillance is carried out by small, unmarked turboprop planes with hidden state-of-the-art sensors that fly thousands of kilometres between air bases and bush landing strips across the vast continent, the Washington Post reported on Wednesday.

The programme, dating back to 2007, underscores the massive expansion of US special forces operations in recent years and the steady militarisation of intelligence operations during the decade-long war on al-Qaeda.

Bases in Burkina Faso and Mauritania are used to spy on al-Qaeda in the Islamic Maghreb (AQIM), while bases in Uganda are used in the hunt for the Lord's Resistance Army, a brutal guerrilla movement led by Joseph Kony, who is wanted for war crimes by the International Criminal Court.

Kony hunt

The paper said there were plans to open another base in South Sudan to help hunt for Kony, who is wanted in connection with a series of atrocities and operates in some of the most remote and inaccessible parts of central Africa.

In East Africa, US aircraft operating out of Djibouti, Ethiopia, Kenya and the Seychelles archipelago spy on Somalia's Qaeda-inspired Al-Shebab militia and have reportedly launched attacks on wanted fighters.

The paper said the fleet of surveillance planes was made up of single-engine Pilatus PC-12s, small passenger and cargo planes manufactured in Switzerland.

The newspaper said one of the secret bases was in a secluded hanger in Ouagadougou, capital of the predominantly Muslim country of Burkina Faso in West Africa.

It said dozens of service members and contractors strived to be discreet, but stood out in the city centre and were appreciated for the business they brought to bars and restaurants.

Burkina Faso's Foreign Minister Djibril Bassole, in an interview with the paper, declined to answer questions about US special forces operations in his country but said he appreciated US security co-operation.

"We need to fight and protect our borders," the paper quoted him as saying. "Once they infiltrate your country, it's very, very difficult to get them out," he said, referring to al-Qaeda.