Romania said Iranian warships opened fire and seized a Romanian oil rig Tuesday off the coast of Iran, holding its workers for hours in an incident stemming from a commercial dispute.

Sergiu Medar, a national security adviser to Romanian President Traian Basescu, said the seizure resulted from a commercial disagreement that Iran is treating “in an extreme way.” He gave no details.

The crew of 27 was held for several hours on the rig’s heliport before being freed following demands from Romania’s Foreign Ministry, according to Gabriel Comanescu, president of the private company GSP, which owns the rig. Iran has not commented on the incident.

GSP said a number of Iranian warships fired in the direction of the rig, and troops from the vessels boarded and seized it. Comanescu said one of the cranes was destroyed in the attack.