The cargo-laden vessel was en route to Somalia from Asia when it was seized over the weekend, said Noel Choong, head of the International Maritime Bureau's piracy reporting center in Kuala Lumpur.
The bureau only received a distress report from a third party on Monday and is still verifying the time and date of the attack, he said. No further details were immediately available.
The attack comes despite increased international cooperation to crack down on pirates in the African waters.
"It shows that the momentum is still there, the attacks are still continuing in this key shipping route," Choong said, adding that the bureau has issued a warning for ships to maintain a strict watch to thwart the bandits.
The hijacking pushed the number of attacks this year in the African waters to 74. A total of 30 ships have been hijacked, and 10 remain in the hands of pirates along with nearly 200 crew members, Choong said.
Momentum has been growing for coordinated international action following the Sept. 25 hijacking of the Ukrainian ship MV Faina, which was carrying tanks and other heavy weaponry.
NATO has sent warships to the area to help U.S. navy vessels already patrolling the region. India also announced it will send warships to the area, and several European countries have said they would launch an anti-piracy patrol.
Some naval commanders are also suggesting shipping companies hire private security firms to counter possible hijackings.
Somalia, which has not had a functioning government since 1991, has been impoverished by decades of conflict, and piracy by Somali gangs has emerged as a lucrative racket that brings in millions of dollars in ransoms. A Russian warship was moving through the Suez Canal Tuesday to join military vessels from other nations protecting shipping in pirate-infested waters off Somalia, a navy official said.
Russian Navy spokesman Capt. Igor Dygalo said the guided missile frigate Neustrashimy (Intrepid) will join warships from other nations surrounding an arms-laden Ukrainian vessel seized by Somali pirates three weeks ago.
The Russian deployment has raised media speculation that Moscow, which has dealt harshly with hostage-takers in the past, could use force to free the crew of the MV Faina.
Dygalo refused to comment on the speculation. He said the Russian ship may coordinate its action with other foreign vessels, but wouldn't give further details.
The Neustrashimy mission reflects a growing readiness by Moscow to project its power worldwide.
"The Russian ship will fulfill the task of minimizing the threat of pirate attacks," Dygalo said in a statement. He added that it will "join the action of foreign navy ships currently controlling the situation around the ship."
The hijacking of the Faina, one of 29 ships seized in the pirate-infested waters off the Gulf of Aden this year, raised concern that the sensitive cargo could fall into the hands of al Qaeda-linked insurgents in Somalia.
U.S. warships have been surrounding the Faina, aiming to prevent the pirates attempting to offload the ship's cargo of more than 30 tanks and other weapons.
The pirates have lowered an initial ransom demand from US$20 million to US$8 million and have withdrawn a threat to blow up the vessel if they don't receive the sum.
Dygalo said that the level of cooperation between the Neustrashimy and foreign warships in the area - "from coordination of actions to concrete practical measures" - will be determined by Russian diplomats and military officials.
The continued seizures of vessels - despite the presence of U.S. and other warships - highlights the difficulties of patrolling the waters off Somalia. The chief concern is that the brazen attacks could fuel terrorism and make one of the world's major shipping routes too dangerous and expensive to traverse.
Somalia, with no effective government since 1991, is not able to guard its long coastline.
Dygalo said that Russia will continue to send its ships on a regular basis to the Horn of Africa to "counter a threat to the shipping and lives of Russian sailors."
Vladimir Putin, now prime minister, sought to restore Russia's global power and prestige during his eight years as president. His successor, President Dmitry Medvedev, recently pledged to send Russian forces on regular deployments worldwide.