Worldwide sea piracy falls to lowest level in four years following international warship patrols in the Gulf of Aden

Attempted hijackings fell from more than 350 to 233 in the first nine months of this year

Worldwide sea piracy has fallen to its lowest levels in four years, according to the International Maritime Bureau, with attacks off the coast of Somalia falling sharply.

Attempted hijackings fell from more than 350 to 233 in the first nine months of this year, with the bulk of that drop coming off the Horn of Africa where there were 70 attacks versus nearly 200 in the same period of the previous year.

An international armada of warships has been patrolling the Gulf of Aden and the Indian Ocean waters off Somalia in an attempt to quell a crisis that had threatened global shipping. In the last 18 months armed guards have been placed on many cargo ships and the US and EU have stepped up their naval presence, while other nations including India and China have sent vessels.

“We welcome the successful robust targeting of pirate action groups by international navies in the high-risk waters off Somalia,” said IMB director Pottengal Mukundan who called for the patrols to be maintained.

However, security sources in the region said that the fall in the number of attacks was as much to do with pirate gangs ransoming off previous hijackings, and poor weather conditions, as a major breakthrough in anti-piracy efforts.

“There's a lot of stock clearance going on where deals are being done for old boats and crews,” said a security source in Nairobi, speaking on condition of anonymity. “The pirates are waiting for the dust to settle and waiting out the expensive naval operations.”

Somali pirates are still holding 11 foreign vessels for ransom with at least 167 crew members. Three ransom deals have been struck in the last week, supporting the “stock clearance” theory, while calmer weather is also due in the coming weeks.

Kenya has attempted to take credit for the piracy dip, claiming its forces' capture of the southern Somali port city of Kismayo had contributed to improved security. But the main pirate ports – such as Eyl and Hobyo – are further north on Somalia's 3,000km coastline and pirates were not known to be operating from Kismayo when it was under the control of Islamic militants, al-Shabaab.

Billions of dollars of goods and up to four per cent of the world's oil supply pass through the Gulf of Aden between Yemen and Somalia.

Somalia has not had an effective coastguard during much of its 20-year civil war that followed the collapse of its central government in 1991.