NAIROBI, Kenya – Signaling a new offensive mindset, international military officials vowed Friday to fight the pirates as swarms of Somalis moved into the waters off East Africa. Four shootouts with pirates showed that high-seas attacks are intensifying with the end of the monsoon season.

Nearly half the 47 ships hijacked off Somalia last year were taken in March and April — the most dangerous months of the year for ships in the Gulf of Aden and Indian Ocean.

In the most serious skirmish Friday, six pirates attacked a vessel before breaking off and chasing the French fishing boat Torre Giulia, said Cmdr. John Harbour, spokesman for the EU Naval Force.

A French military detachment onboard a nearby ship fired warning shots at the pirates. The ship then approached the skiff and collided with it, sinking the skiff and throwing the pirates into the water. Four were rescued, but two others were missing, Harbour said.

The French Defense Ministry said its frigate, the Nivose, intercepted 22 suspected pirates Friday in two separate operations.

Each case, in different sectors, involved a mothership and two “assault skiffs,” a ministry statement said.

Harbour said a spike in attacks is likely in the coming weeks. This season, though, ship owners and sailors are more prepared to evade pirates, fight back, or they have armed security onboard, raising the likelihood of violence.

“We know the monsoon is over. We know they’re coming. We’re taking the fight to the pirates,” said Harbour.

Crews are successfully repelling more attacks, making it harder for pirates to capture ships and earn multimillion dollar ransoms.

In turn, the Somali gangs are increasingly turning violent. The International Maritime Bureau says only seven ships were fired on worldwide in 2004 but that 114 ships were fired on last year off the Somali coast alone.

In a second incident Friday, the EU Naval Force intercepted a pirate group of one mothership and two skiffs that had attacked a separate French vessel. That attack was also repelled by military personnel onboard. The naval force said it destroyed the mothership and one skiff and took 11 pirates into custody.

In the third and fourth attacks, pirates assaulted two Spanish tuna fishing boats off the coast of Kenya, Spain’s Ministry of Defense said. A spokesman said the boats had contacted Spanish navy forces, who dispatched a plane. Between the air support and the private guards on the boats, they repelled the attack.