The HMCS Winnipeg dispatched a Sea King helicopter Saturday that helped stymie a possible pirate attack on an oil tanker around the northern coast of Somalia. (CBC)

The Canadian navy helped ward off suspected pirates from possibly hijacking a commercial vessel around the northern coast of Somalia, a commander said Sunday.

HMCS Winnipeg dispatched its Sea King helicopter on Saturday after three small boats chased the oil tanker Pacific Opal in the Gulf of Aden, where piracy is rampant.

The helicopter crew warned the suspected pirates by hanging a sign that read "stop" in Somali outside the chopper's cargo door next to the machine gun, Cmdr. Craig Baines said.

"As soon as the vessels saw the helicopter, they immediately stopped what they were doing and let the vessel carry on its way," he said.

The Sea King stayed with the Pacific Opal until the threat was gone, Baines said.

Piracy is rampant around the coast of Somalia, which has not had a functioning government for 18 years. There were 115 reported pirate attacks last year, each demanding an average ransom of $1.5 million, according to the Canadian Defence & Foreign Affairs Institute.

Within hours of averting the possible hijacking, HMCS Winnipeg also helped a boatload of 51 Somali refugees, including women and children, who were trying to cross the gulf to Yemen.

The refugees, who had been at sea for about two days, were given food and water before continuing on their way, Baines said.

HMCS Winnipeg is currently participating in a NATO-led counter-piracy mission known as Operation Allied Protector, part of an effort by the international community to restore safety to a major shipping lane that passes by the Horn of Africa.

With a crew of approximately 240 officers and non-commissioned members, the 134-metre long patrol frigate has been at sea since Feb. 5 and won't return to Victoria until Aug. 21.

With files from the Canadian Press