UPDATE 1-Pirate attacks by heavily armed gangs surge off Nigerian coast
* Pirates often violent - International Maritime Bureau
* Ship crews face rising threat of kidnappings off W.Africa
(Adds comment from Nigerian navy)
LONDON, Oct 17 (Reuters) - Pirate attacks off Nigeria's coast have jumped by a third this year with ships passing through West Africa's Gulf of Guinea, a major commodities hub, increasingly under threat from gangs wanting to snatch cargoes and crews.
Unlike the dangerous waters off Somalia and the Horn of Africa on the east coast of Africa, through which ships now speed with armed guards on board, many vessels have to anchor to do business off West African countries, with little protection.
This makes them a soft target for criminals and jacks up insurance costs.
"Pirates, often heavily armed and violent, are targeting vessels and their crews along the (Nigerian) coast, rivers, anchorages, ports and surrounding waters. In many cases, they ransack the vessels and steal the cargo, usually gas oil," the International Maritime Bureau (IMB) reported on Thursday.
Countries on the Gulf of Guinea, including Nigeria, Ghana and Ivory Coast, are major sources of oil and cocoa and increasingly metals for world markets.
Data from the IMB, which coordinates the fight against maritime crime and malpractice, showed Nigeria remained the main source of piracy in the region with 29 attacks on vessels recorded in the first nine months of 2013, up from 21 in the same period last year.
There were four separate attacks around Ivory Coast this year versus three in the 2012.
Analysts say while Somali gangs have focused on capturing vessels to extract ransom money, criminality in West Africa, including oil theft, poses more complex problems.
In a separate report last week Denmark-based security firm Risk Intelligence estimated 117,000 tonnes of oil products worth around $100 million had been stolen by pirate gangs in the Gulf of Guinea since 2010. This includes the diesel known as gas oil.
In June, West and central African nations agreed to set up a monitoring centre to coordinate efforts to combat piracy.
"We have tracking systems for monitoring boats in our waters from control rooms, we have increased the numbers of patrols and the air force are helping out with aerial monitoring," Nigerian navy spokesman Commodore Kabir Aliyu said.
Authorities had boosted their fleet of counter-piracy patrol boats to 11 vessels from eight previously, Aliyu said.
In August, Nigeria's navy killed 12 pirates in a gun battle as they tried to flee from a fuel tanker they had hijacked. Ghana's navy separately in August intercepted a ship and arrested its crew on suspicion of hijacking a tanker.
"Armed robberies, hijackings and incidences of kidnap for ransom are likely to continue up to, and possibly beyond, 150 nautical miles from the coast," said Rory Lamrock of British-based security firm AKE.
The IMB said in the first nine months of 2013 the Gulf of Guinea accounted for all crew kidnappings worldwide, 32 of them off Nigeria, and two off Togo. In such incidents, sailors are taken ashore and usually held for ransom.
Despite the jump in West Africa, overall global pirate attacks fell in the period to the lowest level since 2006, helped by a slowdown in attacks by Somali groups.
The IMB said there were 188 piracy incidents in the January to September period, down from 233 last year. Hostage-taking had also dropped with 266 people taken this year, compared with 458 in the same period in 2012.
Prompted by soaring costs for shippers, including insurance and the safety of their crews, international navies have stepped up pre-emptive action against pirates, such as strikes on bases on the Somali coast.
Shipping firms are also using armed guards and measures such as better monitoring and razor wire defences.
"Although the number of attacks is down overall, the threat of attacks remains, particularly in the waters off Somalia and in the Gulf of Guinea. It is vital that ship masters continue to be vigilant as they transit these waters," said IMB director Pottengal Mukundan.
(Additional reporting by Tim Cocks in Lagos; Editing by Anthony Barker and Alison Williams)