CAMP LEMONNIER, Djibouti — Piracy has made a worrisome return to the waters off Somalia after a five-year hiatus, U.S. defense officials said, prompting commercial shippers, the military and others to revisit the issue.

In the past two months, there have been as many as six incidents of piracy, according to Gen. Tom Waldhauser, head of the U.S. military’s Africa Command, speaking to reporters here Sunday. They are the first incidents since about 2012, Waldhauser said. Pirates seized food, oil and other commodities from smaller-size boats, he said.