CAMP LEMONNIER, Djibouti — After years of relative calm, piracy is on the rise again off the coast of Somalia, U.S. officials here said Sunday.

Gen. Thomas Waldhauser, the Marine officer in charge of the U.S. Africa Command, said there have been “five or six” piracy incidents in the region in two months.

Waldhauser, speaking at a news conference here with Defense Secretary Jim Mattis, attributed the spike in attacks to the widespread drought and famine gripping the region. He said the ships the pirates were targeting have been small in size and carried goods such as food and oil.

“I wouldn’t say it’s a trend, but we’ll watch it,” he said.

After a coordinated international response to piracy in 2010 and 2011, including additional patrols of U.S. and European naval ships in the waters around Somalia, the number of pirate attacks in the past five years has been negligible.

That has changed in recent months.

“It has certainly increased,” said Navy Capt. Richard Rodriguez, chief of staff of the U.S. task force in the Horn of Africa.

Rodriguez told reporters that the U.S. task force has a monitoring role, while local authorities and units led by the European Union take the lead in assessing the resurgent threat.

An Indian ship was hijacked by pirates this month, just weeks after an oil tanker was seized in nearby waters.

In 2011, there were more than 230 pirate attacks off the coast of Somalia, according to the International Maritime Bureau. In the years since, shipping companies have increased security measures, including using anti-boarding devices and armed contractors to deter pirates.

A defense official, who spoke on the condition of anonymity to discuss intelligence matters, partially attributed the recent spike in pirate activity to complacency among shipping companies, saying they may have relaxed their security procedures in recent years because of the reduction in threat.

Mattis told reporters that the Pentagon would monitor the situation and that measures undertaken by shipping lines appear to be sufficient.

“I don’t see a big military role,” he added.

Mattis’s visit marks the first time a high-ranking Trump administration official has visited Africa and comes as the U.S. military increases pressure on militant groups in the region. In March, President Trump gave the Pentagon new authority to conduct airstrikes against the terrorist group al-Shabab in Somalia, and the U.S. military has conducted about 70 airstrikes against al-Qaeda fighters in Yemen in two months.

Camp Lemonnier, the only permanent U.S. base in Africa, also has continued to expand. In the past 15 years, the base has transformed from an austere Marine outpost to a sprawling military installation with 4,000 U.S. troops and dorm-style barracks. Nearby, the Air Force operates an independent drone base. The United States pays $65 million a year to Djibouti’s government to use Lemonnier. The base’s name is derived from a French Foreign Legion outpost built in the same area in the 1950s.

The base’s strategic location on the Horn of Africa has made it central for U.S. forces in the Middle East and Africa, including help with missions in Yemen and Somalia. Lemonnier also sits just south of the Bab-el-Mandeb Strait, a key choke point between the Horn of Africa and the Middle East that has been the scene of recent naval hostility between Yemeni Houthi rebels and Saudi forces.

While Lemonnier is located near French, Italian and Japanese bases, a new Chinese outpost has raised concern among some U.S. officials. The base, an hour’s boat ride north, is under construction and is likely be used as a hub to help transit natural resources from the continent back to China.

Currently, Marine aircraft from the 24th Marine Expeditionary Unit are staged at Lemonnier to help with operations in the region. The base also serves as a transit hub for U.S. forces working in Somalia. The contingent of about 100 troops there has attempted to bolster the fledging Somali military and its efforts against al-Shabab militants before a coalition of African countries, called AMISOM, fighting al-Shabab withdraws in 2018. U.S. officials, however, have suggested that AMISOM’s withdrawal could be contingent on the Somali military’s ability to conduct operations without support.

According to Rodriguez, there are about 22,000 AMISOM troops in Somalia and 12,000 Somali troops. The Somali military would have to be about the same size as the current AMISOM contingent to effectively counter al-Shabab militants, he said.