A US-sanctioned oil tanker, Sibu 1, has been freed after being hijacked by Somali pirates in August, the maritime police force in Somalia's semi-autonomous Puntland region said on Friday.

"It was a counter-piracy operation that was carried out by our forces from two days ago and it's still going on. The ship is free and the pirates are all in the hands of our forces," Mohamed Jama, a commander in the Puntland Maritime Police Force, told Reuters.

Sibu 1 was seized on August 20 by six armed individuals, according to the United Kingdom Maritime Trade Operations (UKMTO). ​The tanker was placed under sanctions by the US Treasury in December for allegedly being part of a ​shadow fleet that helps Iranian petroleum products evade US sanctions.

Piracy has resurged off Somalia's coast in recent months.

Sibu 1 was at ⁠least the 13th vessel attacked this year off Somalia or in the Gulf of ​Aden, which separates Somalia and Yemen, according to International Maritime Bureau data and UKMTO reports.

A wave of Somali piracy between 2008 and 2014 triggered a security crisis in the western Indian Ocean that cost the global economy billions of dollars and led to hundreds of millions of dollars in ransom payments.