In the first quarter of 2007, 41 incidents were reported while in the same period last year, IMB noted 66 cases.
For the entire 2013, a total of 264 cases were recorded, the lowest level in six years following a sharp drop in attacks by the once notorious Somali pirates.
The piracy watchdog said in the first three months of this year, two vessels were hijacked, 37 vessels boarded and two crew members were kidnapped.
In waters off Somalia, five cases were reported.
"Although the number of attacks continues to remain low, the threat of Somali piracy is still clearly evident," IMB Director Pottengal Mukundan said in a statement.
He cited an incident in January where a Panamax-sized product tanker was fired upon about 115 nautical miles south of Salalah in Oman from a skiff launched from a mother ship.
The attack was thwarted and the international navies patrolling the area managed to intercept the mother ship, an Indian dhow that had been hijacked a few days previously.
The IMB said 11 Indian crew members were freed and five suspected pirates were arrested. The incident, it noted, showed the crucial role played by the international navies in containing the threat of Somali piracy.
"There can be no room for complacency as it will take only one successful Somali hijacking for the business model to return. Masters are therefore advised to maintain vigilance and adhere to the industry's latest best management practices recommended," Mukundan said.
While the Somali pirates were lying low, the Nigerian pirates have expanded their reach to waters off Angola.
IMB said Angola reported its first hijacking, which was blamed on Nigerian pirates.
Indonesia continues to rank as the most piracy-prone place with 18 cases reported in the January-March period. Nigeria was second with six cases. The Straits of Singapore was third with five cases, followed by Bangladesh with four.