(Bloomberg) — Nato will send more naval firepower to fight piracy off the coast of Somalia, agreeing to dispatch six ships to protect sea lanes that handle a tenth of the world's trade.

A "short gap" may ensue between the departure of the current five-ship fleet on June 28 and the arrival of the new task force in July, the North Atlantic Treaty Organisation said after defence ministers endorsed the deployment today.

"Nato will continue to participate in the mission and it might well be that the mission will be beefed up," Secretary General Jaap de Hoop Scheffer told a Brussels press conference.

Patrolling a swathe of water about four times the size of France, warships from Nato, the European Union and countries including Russia and China have battled 114 pirate attacks so far this year, more than in all of 2008.

Put on the defensive by the naval build-up, the pirates have started attacking at night and may be moving from the Gulf of Aden to the southern Red Sea to prey on commercial vessels, the US Navy warned this week.

Armed gangs have seized 29 merchant ships this year, making the seas off violence-scarred Somalia — lacking a functioning government for almost two decades — the world's most treacherous.

Owners of merchant vessels such as oil tankers and container ships are paying as much as $40,000 per passage for security guards on vessels in the pirate-infested waters, said Arild Nodland, chief executive officer of Bergen Risk Solutions. Insurance costs have also advanced, he said.

"We've decided to make the Nato maritime standing group available for counterpiracy to complement the many other assets that are doing this job off the Horn of Africa," U.K. Defence Secretary Bob Ainsworth said.

Warships from the U.S., Portugal, Canada, the Netherlands and Spain make up the current task force, cobbled together from a group that is normally used for routine exercises and port visits.

The follow-up force consists of ships from the US, UK, Greece, Italy and Spain. Germany plans to join.

Russia, its ties with Nato improving after strains due to last year's war with Georgia, may also take part, a Nato official said.

The fleet will patrol for an undetermined period, while the 28-nation alliance wrestles over legal questions such as the treatment of captive pirates before conducting a "longer-term" mission, spokesman James Appathurai said.

The EU force last month widened its patrols as far as the Seychelles islands as the clampdown on Somalia's coastal waters drives pirates further out to sea.

Germany will keep its anti-piracy deployments under the Nato and EU flags capped at 1,400 soldiers and sailors, Defense Minister Franz Josef Jung said.

"It's in our interest that we effectively fight piracy, in the interest of free trade and security on the seas," Jung said.

Using Somalia as a base, gangs that seize commercial ships often hold them for ransom, as when they extorted $43,000 for the release of the 11 crew members of a Nigerian oilfield tugboat on June 6 after a 10-month ordeal.

Reeling from 18 years of civil war, Somalia is struggling to establish a working government and cope with 1 million refugees and 3.2 million people without adequate food, according to the United Nations.

Nato is also looking at the EU's extradition deal with Kenya as a possible model for the handling of captured pirates. Current Nato rules require captives to be treated according to the laws of the country of the ship that seized them.

Under that legal authority, Dutch- and Canadian-flagged warships were forced to set captive pirates free.