CATANIA, Italy - Canada has joined an air war of a different kind in the skies over Libya, one where persuasion and sometimes insults are the weapons.

Canadian CP-140 Aurora surveillance planes recently started broadcasting propaganda messages aimed at forces loyal to Libyan strongman Moammar Gadhafi.

It's a psychological warfare operation, or PSYOPS, initially started by the Americans but now overseen by NATO -- the kind of mission western militaries are reluctant to talk about openly.

The Canadian broadcasts are relatively benign in comparison to some of the harsher messages NATO has aimed at Gadhafi's troops, in which women's voices are telling them to stop "killing the children."

The Canadian messages, in English, are read hourly during patrols along the Libyan coast over AM/FM frequencies that Libyans usually monitor.

"For your safety return to your family and your home," says the message, which can be heard over unencrypted frequencies the military uses to broadcast basic information.

"The Gadhafi regime forces are violating United Nations resolution 1973."

The message goes on to urge Gadhafi's troops not to take part in further hostilities and not to harm their fellow countrymen.

The Libyans have apparently yelled back telling the "Yankee pigdogs" to go home. On at least one occasion last week, an Arabic sounding voice challenged the broadcasts.

"Who are you talking to?" the voice asked.

"Anyone who will listen," replied the other voice who had read the message.

Gadhafi's regime has tried to jam the transmissions.

A Canadian air force spokeswoman wouldn't talk about the broadcasts, calling it "a NATO policy." She referred all questions to the alliance's southern headquarters in Naples.

NATO officials were also reluctant to talk and asked not to be quoted on the record.

"Since the start of operations NATO have been encouraging pro-(Gadhafi) forces to lay down their arms," said one military official on background.

The "NATO mission is to prevent attacks and threats against civilians and we are doing it with care and precision. NATO will continue to keep up the pressure on those forces which are attacking or threatening civilians and civilian populated areas until that violence comes to an end."

The messages are part of a stepped up PSYOPS campaign which is sometimes referred to in the army as the "black art." Italian aircraft dropped propaganda leaflets over Tripoli last May as part of the increased pressure.

At the beginning of the air war, the United States dispatched its secret, specially outfitted C-130J transport plane known as "Commando Solo" to warn Libyan ships to stay in port or risk being destroyed by NATO.

Although propaganda broadcasts have been around a long time and reached their zenith during the Second World War, the use of radio and sometimes television messages broadcast from aircraft to bend the mind of enemies goes back to the Vietnam War era.

The two Aurora surveillance planes, with crews and support teams from Nova Scotia and B.C., were initially tasked with monitoring the sea lanes around Libya to watch for ships trying to skirt the UN arms embargo.

They have also been searching for some of the mines the pro-Gadhafi forces have dropped into the water near major ports.

"We support the maritime commander in whatever he requires," said Maj. Jeff Rodger, the Aurora detachment commander who belongs to 407 Squadron out of Comox, B.C.

But as the Libyan conflict unfolded, the aircraft have been used more for their ability to spy on ground threats and to catalogue possible Gadhafi regime vehicles and command centres.

It is patient and precise work for aircrew who end up on the extended missions that fly right up to the Libyan coastline. Some of the aircrew compared it to cops on a stakeout.

"Sometimes, it just as simply as following something for a while to see where it goes and what it does," said Capt. Jerry Collins, of 405 Squadron, based in Greenwood, N.S.

Occasionally, they end up witnessing battles -- or the aftermath of fighting -- through their high-resolution cameras and sensors.

"They're always jockeying back and forth for position," said Collins. "All we do is take note of it. Times. Places. Positions."

It can be tough sometimes to turn away from the displays. "People are losing their lives," said Collins.

He added that bearing witness and passing information back so that NATO jet fighters can target Gadhafi forces is "why we're here, to make this stops."

The patrols can sometimes be gruelling in the 30-year-old Auroras, which are used for coastal surveillance and fisheries patrols back home.

Designed as an anti-submarine warfare plane, the crews jokingly describe it as a "flying Winnebago" for its 1980s decor and aft kitchen where meals can be taken on long flights.