– Dozens of Somali Islamist insurgents stormed a port on Friday hunting the pirates behind the seizure of a Saudi supertanker that was the world's biggest hijack, a local elder said. Separately, police in the capital Mogadishu said they had ambushed and shot dead 17 Islamist militants, in the latest illustration of the chaos in the Horn of Africa country that has fueled a dramatic surge in piracy. The Sirius Star – a Saudi vessel with a $100 million oil cargo and 25-man crew from the Philippines, Saudi Arabia, Croatia, Poland and Britain – is believed anchored offshore near Haradheere, about half-way up Somalia's long coastline. “Saudi Arabia is a Muslim country and hijacking its ship is a bigger crime than other ships,” Sheikh Abdirahim Isse Adow, an Islamist spokesman, told Reuters. “Haradheere is under our control and we shall do something about that ship.” Some experts fear that the use of force to free the ship could be disastrous. They note that the MV Faina, a Ukrainian ship seized by the same pirates in September with a cargo of tanks and other weaponry, was booby-trapped by the hijackers. Environmental groups have warned of a huge catastrophe if oil from the supertanker was released. Both the US Navy and Dubai-based ship operator Vela International said they could not confirm a media report the hijackers were demanding a $25 million ransom. That would be the biggest demand to date by pirates who prey on boats in the Gulf of Aden and Indian Ocean off Somalia. A pirate identifying himself as Jamii Adam told Asharq Al-Awsat newspaper that negotiations were taking place with the ship's owners, saying the ransom demanded was not excessive but declining to give a figure. He said it had cost the pirates $500,000 to seize the vessel. “We bore many costs to hijack it,” he said. In Mogadishu, police said they laid in wait and shot dead 17 fighters from the militant Al-Shabaab insurgent group during an attempted attack on a senior official. The Islamists have been fighting the government and its Ethiopian allies for about two years. They launch near-daily guerrilla strikes in the capital and control most of the south, including a town just nine miles (14 km) from Mogadishu. Islamist leaders deny allegations they collude with pirates and insist they will stamp down on them if they win power, citing a crackdown when they ruled the south briefly in 2006. Some analysts, however, say Islamist militants are benefiting from the spoils of piracy and arms shipments facilitated by the sea gangs. Analysts also accuse government figures of collaboration with pirates. The elder in Haradheere port told Reuters the Islamists arrived wanting to find out immediately about the Sirius Star, which was captured on Saturday about 450 nautical miles off Kenya in the pirates' furthest strike to date. “The Islamists arrived searching for the pirates and the whereabouts of the Saudi ship,” said the elder. “I saw four cars full of Islamists driving in the town from corner to corner. The Islamists say they will attack the pirates for hijacking a Muslim ship.” In Mogadishu, Al-Shabaab gunmen drove to the home of the local Madina district chairman early in the morning, but found police officers lying in wait, witnesses said. “We got information before they left their hideouts and we were able to surround them,” said a police spokesman. “Thirteen of the dead bodies lie in the street near the chairman's house.” Washington has listed Al-Shabaab as a foreign terrorist organization with close links to Al-Qaeda. It does not have deep popular support, despite having the upper hand militarily. Somalia has been without effective central government since the 1991 toppling of military dictator Said Barre by warlords. An upsurge of attacks this year has forced up shipping insurance costs, made some firms go round South Africa instead of via the Suez Canal, brought millions in ransom payments, and prompted an international naval response. Iran's biggest shipping firm said gunmen holding a Hong Kong-flagged ship carrying wheat and 25 crew members had set demands for its release, but it did not reveal what they were. Pirates released a Greek-owned ship with 19 Romanian crew on board which had been hijacked in September, Andrew Mwangura of the East African Seafarers' Association said on Friday. “I understand that some ransom was paid from Romania, but the amount is unknown,” he said. The capture of the Sirius Star has caused panic around the world, with the rampant piracy threatening to become a further drag on trade at a time of global economic downturn. Kenya's Foreign Minister Moses Wetangula summoned foreign ambassadors in Nairobi to appeal for their countries to make all efforts to end the menace. “Act now and not tomorrow,” he said.