An Indian naval vessel sank a suspected pirate ‘mother ship' on Wednesday in the Gulf of Aden and chased two attack boats into the night, officials said, yet more violence in the lawless seas where brigands are becoming bolder and more violent. Separate bands of pirates also seized a Thai ship with 16 crew members and an Iranian cargo vessel with a crew of 25 in the Gulf of Aden, where Somalia-based pirates appear to be attacking ships at will, said Noel Choong of the International Maritime Bureau's piracy reporting center in Malaysia. “It's getting out of control,” Choong said. A multicoalition naval force has increased patrols in the region, and scored a rare success on Tuesday when the Indian warship, operating off the coast of Oman, stopped a ship similar to a pirate vessel mentioned in numerous piracy bulletins. The Indian navy said the pirates fired on the INS Tabar after the officers asked it to stop to be searched. “Pirates were seen roaming on the upper deck of this vessel with guns and rocket-propelled grenade launchers,” said a statement from the Indian navy. Indian forces fired back, sparking fires and a series of onboard blasts - possibly due to exploding ammunition - and destroying the ship. They chased one of the two speedboats that had been shadowing the larger ship, and which fled when it sank. One was later found abandoned. The other escaped, according to the statement. Larger ‘mother ships' are often used to take gangs of pirates and smaller attack boats into deep water, and can be used as mobile bases to attack merchant vessels. Tuesday incidents raised to eight the number of ships hijacked this week alone, he said. Since the beginning of the year, 39 ships have been hijacked in the Gulf of Aden, out of 95 attacked. Choong said 17 vessels remained in the hands of pirates along with more than 300 crew members, including a Ukrainian ship loaded with weapons and a Saudi Arabian supertanker carrying $100 million in crude. Despite the stepped-up patrols, the attacks have continued unabated off Somalia, which is caught up in an insurgency and has had no functioning government since 1991. NATO has three warships in the Gulf of Aden and the US. Navy's Bahrain-based 5th Fleet also has ships in the region. But US Navy Commander Jane Campbell of the 5th Fleet said naval patrols simply could not prevent attacks given the vastness of the sea and the 21,000 vessels passing through the Gulf of Aden every year. The Thai boat, which was flying a flag from the tiny Pacific nation of Kiribati but operated out of Thailand, made a distress call as it was being chased by pirates in two speedboats but the phone connection was cut off midway. Wicharn Sirichaiekawat, manager of Sirichai Fisheries Co., Ltd. told The Associated Press that the ship, the ‘Ekawat Nava 5,' was headed from Oman to Yemen to deliver fishing equipment. Of the 16 crew members, Wicharn said 15 are Thai and one is Cambodian.