The response will need to come from the country where the tanker is registered/flagged. Liberia and Panama aren't exactly known for their Navy fleets. Without that, it's up to the ship's commercial owner to resolve, or more likely, their insurance company.
The crew are rarely trained and equip to respond to an armed attack. If they have anyone to defend the ship, at most it's a handful of mercenaries hired for the high risk part of the trip.
The crew are rarely trained and equip to respond to an armed attack. If they have anyone to defend the ship, at most it's a handful of mercenaries hired for the high risk part of the trip.