Boko Haram kidnapped more than 200 schoolgirls in May 2014. Boko Haram, which means “Western education is forbidden,” was designated as a terrorist group by the U.S. government in 2013. (Akintunde Akinleye/Reuters)

The White House announced Wednesday that it is deploying 300 U.S. troops to Africa to set up a drone base to track fighters from Boko Haram, the network of Islamist extremists that has destabilized Nigeria and neighboring countries during a long and bloody uprising.

The U.S. forces will be based just to the east of Nigeria in Cameroon, where they will operate a small fleet of unarmed Predator drones that will conduct surveillance across the region, according to the Defense Department. About 90 troops arrived Monday, with the remainder expected in the next several weeks.

Boko Haram has been waging a vicious insurgency for several years that originated in Nigeria but has since spilled into neighboring Cameroon, Chad and Niger and left an estimated 20,000 people dead.

Although the group has not targeted U.S. interests, the Obama administration has become increasingly concerned that the threat could spread. Boko Haram leaders pledged allegiance earlier this year to the Islamic State; both groups are fighting to establish a caliphate across the Middle East and Muslim lands in Africa.

“We obviously take the threat, the terror threat from Boko Haram in Africa, seriously,” Josh Earnest, the White House press secretary, told reporters.

The deployment marks the most direct U.S. involvement to date in the campaign against Boko Haram.

The Pentagon deployed one surveillance drone and 80 U.S. troops to Chad in May 2014 to help locate more than 200 missing schoolgirls who had been kidnapped by Boko Haram. But that mission ended after several months.

The U.S. military also flies unarmed drones from Niger, but those surveillance aircraft are dedicated to flights over the Sahara to spy on other Islamist extremists in North and West Africa, not Boko Haram.

Navy Lt. Cmdr. Anthony Falvo, a spokesman for the U.S. Africa Command, declined to identify where exactly the U.S. troops would be stationed in Cameroon. He said the U.S. military was still examining the suitability of setting up a drone base at “a temporary location” in the country.

He said the U.S. troops would also help to train Cameroonian forces to enhance border security and improve intelligence collection. The mission, he added, had been approved by the government of Cameroon.

“We will remain as long as our presence is requested,” Falvo said.

The U.S. troops will be armed with weapons “for the purpose of providing their own force protection and security,” according to a letter that President Obama sent to Congress on Wednesday. But they are not expected to engage in direct combat.

The epicenter of the fight against Boko Haram has been in Nigeria. But the Obama administration has been reluctant to provide substantial military or counterterrorism assistance to the Ni­ger­ian military, which has a long record of human rights abuses.

Nigeria is in the process of establishing a multinational force to fight Boko Haram with soldiers from Cameroon, Chad, Niger and Benin. According to local officials, the United States, France and China have all pledged to offer training.

Last month, the White House announced that it would provide $45 million in military aid to help the regional force combat Boko Haram.

Boko Haram, which means “Western education is forbidden” in the local Hausa language, was designated as a terrorist group by the U.S. government in 2013. It has embraced brutal tactics — bombings, beheadings and kidnappings — to seize control of large parts of northern Nigeria.

Obama is sending three times as many troops to Cameroon as he has assigned to another counterterrorism mission in a different part of Africa — the hunt for Joseph Kony, the guerrilla leader of the Lord’s Resistance Army.

About 100 U.S. Special Operations troops are working in Uganda, Congo, South Sudan and the Central African Republic to track Kony. That mission began in October 2011, and Obama is expected in the coming days to extend it for at least another year.

Over the past eight years, the Pentagon has gone from having virtually no military presence in Africa to running an extensive network of small bases and camps, many of which are focused on surveillance operations.

In addition to Cameroon and Niger in West Africa, the U.S. military flies drones from Ethi­o­pia and Djibouti, where it has a large counterterrorism base on the Horn of Africa.

The Pentagon also operates manned surveillance aircraft from Uganda and Burkina Faso.