Somali piracy has returned at a scale not seen for more than a decade, with at least 13 ships attacked since the start of the year and two cargo vessels seized in the Gulf of Aden within four days last week. Omar Mahmood, senior Somalia analyst at the International Crisis Group, described piracy as a crime of opportunity and said the pirates can currently see one. That opportunity has been created further north, where the United States and Iran continue to fight over the Strait of Hormuz and Tehran's Houthi allies in Yemen have imposed a targeted blockade of the Bab al-Mandab Strait in a dispute with Saudi Arabia. Vice-Admiral Ignacio Villanueva Serrano, who commands the European Union naval force protecting shipping off Somalia, said the pirates appear to believe international forces are tied up in those crises. Fewer patrols have coincided with more traffic hugging the Somali coast as ships divert south, and with oil prices high a hijacked tanker is a richer prize. Among the recent captures was the Cameroon-flagged MV Lutuf, boarded off Puntland on 17 August, followed days later by the Eritrean-flagged tanker MT Sibu 1 in waters near Yemen. The Lutuf seizure has drawn in outside force: 13 men said to belong to a supply network for the pirates have been killed in two drone strikes since 18 August, nine of them on Sunday. Puntland's deputy security minister, Abdirahman Yusuf, told the BBC Somali Service his administration had evidence Turkey was responsible, and security sources said the ship carried weapons and satellite equipment bound for Turkish operations in Mogadishu. Turkey's defence ministry said only that its forces were providing necessary support to Somali authorities. Six vessels are now being held for ransoms of millions of dollars, four anchored near Bander Beyla, well short of 2011, when Somali pirates mounted more than 200 attacks.