MOGADISHU, Somalia — Pirates off the coast of Somalia have seized an oil tanker with eight Sri Lankans on board, in what is believed to be the first hijacking of a large commercial vessel in the region since 2012, officials said on Tuesday.

The merchant ship was intercepted while en route to Mogadishu, the Somali capital, from Djibouti, and was diverted toward Alula, a port in the semiautonomous Puntland region in northeastern Somalia, Ali Shire Mohamud Osman, the district commissioner in Alula, said in a telephone interview.

The ship’s crew sent a distress signal on Monday evening, saying the vessel was being approached by high-speed boats.

Abdikamil Moalin Shukri, a spokesman for the Ministry of Interior and Security, said the agency was awaiting more details.