UPDATE: The Somali pirates released the crew on Thursday after disembarking without incident, local officials said.

MOGADISHU, Somalia -- Somali pirates who seized an oil tanker opened fire Thursday on naval troops from the semiautonomous state of Puntland, sparking clashes between the two sides, a local official said.

Ali Shire Mohamud, the commissioner of Alula district where the ship is being held, said the clashes started after naval forces tried to stop a boat carrying reinforcement pirates to the ship. Mohamud declined to give further details.

Puntland dispatched naval forces to the area after the pirates seized the ship on Monday. The European Union anti-piracy operation in the region says the pirates are holding the eight Sri Lankan crew members captive and demanding a ransom.

The hijacking of the Comoros-flagged tanker Aris 13 was the first such seizure of a large commercial vessel off Somalia since 2012. International anti-piracy patrols on the crucial trade route had calmed such attacks, which once numbered in the hundreds.

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A security official said one soldier was seriously injured in Thursday’s clashes. The official, who spoke on condition of anonymity because he was not authorized to speak to the media, said pirates on the ship were continuing to receive reinforcements while regional forces mobilizing nearby in an effort to free the ship.

A Somali pirate who said he was in touch with the armed men, Bile Hussein, said the pirates moved the ship away from the coast after naval forces approached.

“The ship and crew will remain safe as long as no one attacks them,” Hussein said by phone from an undisclosed location in northern Somalia.

Families of the crew members tearfully pleaded Wednesday for the men to be released unharmed.

Somali pirates usually hijack ships and crew for ransom. They don’t normally kill hostages unless they come under attack.

The ship had been carrying fuel from Djibouti to Somalia’s capital, Mogadishu, on Monday when it was approached by men in two skiffs and the tanker issued a call for help.