The yacht managed to evade the attempted attack, the International Maritime Bureau (IMB) Piracy Reporting Centre based in Kuala Lumpur said.
The attack took place 78 nautical miles off the island's south west coast early morning on August 18 but was reported by the IMB only on Tuesday.
It did not say whether the fishing boats were Sri Lankan.
The IMB, a specialised division of the International Chamber Of Commerce, is a non-profit making organisation, established in 1981 to act as a focal point in the fight against all types of maritime crime and malpractice.
The IMB Piracy Reporting Centre in Kuala Lumpur, Malaysia maintains a round-the-clock watch on the world’s shipping lanes, reporting pirate attacks to local law enforcement and issuing warnings about piracy hotspots to shipping.
It advises shipping to maintain anti-piracy watches and to report all pirate attacks and suspicious m