The Obama administration is assembling a constellation of secret drone bases for counterterrorism operations in the Horn of Africa and the Arabian Peninsula as part of a newly aggressive campaign to attack al-Qaeda affiliates in Somalia and Yemen, U.S. officials said.

One of the installations is being established in Ethi­o­pia, a U.S. ally in the fight against al-Shabab, the Somali militant group that controls much of that country. Another base is in the Seychelles, an archipelago in the Indian Ocean, where a small fleet of “hunter-killer” drones resumed operations this month after an experimental mission demonstrated that the unmanned aircraft could effectively patrol Somalia from there.

The U.S. military also has flown drones over Somalia and Yemen from bases in Djibouti, a tiny African nation at the junction of the Red Sea and the Gulf of Aden. In addition, the CIA is building a secret airstrip in the Arabian Peninsula so it can deploy armed drones over Yemen.