Somali pirates hijacked a Greek and a Ukrainian ship on Saturday and a NATO warship briefly detained 19 pirates armed with high explosives after foiling an attack on a Norwegian tanker in the Gulf of Aden. Pirates said they were taking the Ukrainian ship, hijacked in the Indian Ocean with a cargo including United Nations' vehicles, to the Somali coastal town of Haradheere. “We have hijacked a ship carrying industrial equipment including white cars with the UN logo, our friends are on board it,” a pirate who said his name was Hussein told Reuters by telephone from Haradheere. Maritime and UN officials were not immediately available to confirm the hijack. Pirates are now holding 17 ships and around 300 crew, including the Greek-owned cargo ship Ariana, hijacked overnight with its Ukrainian crew. Meanwhile, a Portuguese frigate captured 19 Somali pirates after foiling an attack on an oil tanker but released them all, North Atlantic Treaty Organization (NATO) officials said Saturday. Commander Chris Davis, from the control center for the NATO mission protecting merchant ships off Somalia, said the frigate Corte Real launched a helicopter Friday after being informed of an attack on the tanker, the Bahamas-flagged Kition. The helicopter pursued the pirates back to their mother ship, a fishing boat which was later boarded and weapons including grenade-launchers and explosives were seized, Davis said. However a Portuguese officer with the NATO force in the Gulf of Aden, Santos Ferreira, told TSF radio that the 19 pirates captured had been released “after contact was made with Somali national authorities.” It was the first time NATO forces found pirates armed with raw explosives, Lt. Cmdr. Fernandes said from the Portuguese frigate the Corte-Real, which responded to the attack. The Corte-Real had sent a helicopter to investigate a distress call from the Greek-owned and Bahamian-flagged Kition late Friday about 100 miles (161 kilometers) north from the Somali coast in the Gulf of Aden.The suspects fled to a larger pirate vessel without damaging the Kition, but were intercepted by the warship an hour later. The seizure of explosives from the group that attacked the crude oil tanker MV Kition may indicate the pirates are adapting their tactics as crews become better trained in counter-piracy measures. Sailors are aware that pirates generally attack during the day and that some guidelines suggest designating a safe room with a bulletproof door where crews can lock themselves in case of an attack. Such a room would still be vulnerable to being blown open with explosives. Davis said in another incident on Thursday a Turkish vessel, the Christina A, was attacked by pirates in two boats off the Kenyan port of Mombasa, but managed to shake them off by increasing speed to 20 knots. The Kenyan-based East African Seafarers Assistance Program said pirates had seized a bulk carrier in the Indian Ocean, 250 nautical miles southwest of the Seychelles.