The HMAS Toowoomba answered an emergency call from merchant vessel BBC Portugal after it sighted an armed boat approaching on Sept. 20, Australia's Department of Defence said today in a faxed statement. Along with the grenade launcher, staff from the Toowoomba found six AK47 assault rifles, a G3 assault rifle and a large quantity of ammunition.

Somali pirates venturing out to sea as monsoon winds abate are being met by an increased naval presence from the U.S., Pakistan, Turkey, South Korea and Australia. Pirates have attacked vessels off the coast of Somalia about 140 times this year, with a surge in April and May, the U.S. Navy said Sept. 16.

The occupants of the Somali ship denied they planned to attack the BBC Portugal, the department said. The ship was directed to leave the shipping lanes and return to Somalia, Commander Ivan Ingham said.

Naval forces have encountered 542 suspected pirates this year, releasing 315 and turning 212 over for prosecution. Eleven presumed pirates have been killed in the encounters. Four are still being held while their status is investigated.

Pirate attacks early in the year focused on the Gulf of Aden, a choke point for the Suez Canal that's used by 33,000 ships a year. With naval forces patrolling a security corridor through the Gulf, pirates in March shifted their attacks farther out into the Indian Ocean off the east coast of Somalia.

The Toowoomba is an Anzac Class long-range frigate equipped for air defense, surface and undersea warfare and surveillance. It's capable of carrying a Sikorsky Seahawk helicopter to enhance its anti-submarine, anti-surface warfare and search and rescue capabilities, according to its Web site.