MAPUTO, Mozambique (AP) — Seven people beheaded this week. Attacks on homes, schools, health clinics. Thousands of people displaced by the violence. Insecurity that threatens multi-billion dollar investments.

This is the growing problem of Islamic extremist violence in northernmost Mozambique.

Confronted by rising violence, thousands of Mozambicans are fleeing troubled areas of northern Mozambique as the government and humanitarian agencies scramble to provide safe shelter.

Companies investing billions of dollars to pump liquified natural gas in the region are looking at increased risks and costs to protect their investments.

Some 500 people have been killed, many of them beheaded, since the extremists started their attacks in Oct. 2017. Not much is known about the rebels, but last year they became allied with the Islamic State group, which now issues claims of responsibility for attacks.

More than 100,000 have been displaced by the extremist violence, the U.N. refugee agency announced Friday.

A spike in extremist attacks in recent weeks have made it “the most volatile period since the incidents began in October 2017,” the refugee agency’s spokesman Andrej Mahecic said at a press conference in Geneva.

“Attacks are now spreading toward the southern districts of Cabo Delgado,” with one of the latest incidents happening just 100 kilometers (62 miles) from Pemba, the provincial capital which has so far been untouched by the violence.

Seven people were beheaded earlier this week as the armed rebels cut a swathe through the Quissanga district, heading south then east toward the Indian Ocean coast and the islands of the Quirimbas archipelago.

A handwritten letter, purporting to be from the “Armed forces of Ali Xababe (Al Shabaab)” and circulated on social media Friday, said the rebels plan to continue to move south as far as the Mieze high security prison outside Pemba, where many of those arrested on suspicion of involvement in the insurgency are held.

More than 156,000 people have been affected by the insurgency, the Cabo Delgado provincial government said this week. The attackers have burned houses and have laid waste to 76 schools and at least five health centers, according to the provincial government.

An integrated humanitarian response for the province, with support from Swiss Cooperation, is being drawn up by the provincial authorities.

The U.N. refugee agency’s Mahecic said on Friday that the organization would now take over coordinating “all protection activities in partnership with the government,” and would deploy ”additional aid and staff to meet the need, initially for 15,000 internally displaced people and host communities in the coming weeks.”

The violence is also hurting progress on the multi-billion dollar liquified natural gas projects in the north of the province, which are expected to multiply the size of Mozambique’s economy many times over in the coming years.

France’s Total and American ExxonMobil, who operate the two onshore gas liquefaction projects, have asked the Mozambique government to send more troops to protect their installations, according to local press reports. The head of Mozambique’s National Petroleum Institute, which regulates the industry, said on Thursday that the insecurity is inevitably raising costs for the projects — which they may be able to recoup from the taxes paid on gas production when the projects come onstream in the middle of this decade.

The country’s Defence Minister today denied rumors that young men were being forced to join the army, in outlying neighborhoods of the capital, Maputo, and neighboring Matola, the country’s largest city.

“At the moment we have no need for any compulsory recruitment, because we have sufficient forces to guarantee public order and tranquility — both in the theater of operations in the north, and in the center,” where sporadic attacks by former Renamo fighters are causing insecurity on the country’s highways, Minister Jaime Neto told public broadcaster Radio Moçambique.