Dutch commandos on board the frigate Zeven Provinciën in the Gulf of Aden have freed 20 fishermen whose vessel was hijacked by Somali pirates and used to launch an attack against a tanker, the BBC reports.

The captives, all Yemeni, were freed when Dutch forces chased pirates back to the fishing boat, the BBC said. They had been held hostage since Sunday.
Nato spokesman Alexandre Santos Fernandes said the pirates were set free because Nato had no right to detain them.
Dutch law
‘They can only arrest them if the pirates are from the Netherlands, the victims are from the Netherlands, or if they are in Netherlands waters,’ he told Reuters news agency.
The frigate, which has been serving in the region since March, went to the aid of the tanker after hearing a distress call. Commander Ruud Ramaekers told Nos tv that the pirates gave themselves up without a struggle.
The frigate was involved in the capture of seven pirates three weeks ago.
The BBC says pirates are currently holding more than 280 crew members and 15 cargo ships in the region.