BEIJING (AFP) - China is investigating two Canadian Christian activists for alleged espionage, state media and their son said Tuesday, a week after Ottawa accused Beijing of cyber-spying.

Kevin Garratt and Julia Dawn Garratt "are under investigation for suspected theft of state secrets about China's military and national defence research," the state-run Xinhua news agency reported.

The two run Peter's Coffee House, a coffee shop in Dandong, on the border with North Korea, their son Simeon told AFP.

Pictures of the cafe, which overlooks the Yalu river and the Friendship Bridge linking the two countries, show the "T" in its name is in the shape of a crucifix, with a backdrop resembling a stained-glass window.

China's definition of state secrets can be very broad, and the Xinhua report did not specify what was allegedly stolen, adding only that the probe was being conducted by the State Security Bureau in Dandong.

The Dandong region is a sensitive military area for China, and the border crossing is a key trade lifeline for nuclear-armed, diplomatically isolated North Korea.

It is also a focus for foreign Christian groups, including some from South Korea, with some working to assist North Koreans who secretly cross the border to escape from hardship and repression in their homeland.

Mr Simeon Garratt described his parents as "openly Christian" and said they had been involved in sending goods such as oil and cooking supplies to impoverished North Korea to "help basically what they feel is a group of people that have been severely neglected".

"I just think it's crazy," Mr Garratt, 27, who runs a software company in Vancouver, said of the investigation, adding that he had been unable to contact his parents.

"It sounds like something somebody made up," he said. "I really don't know why. It's just so absurd."

On its website the coffee shop describes itself as "only metres from the border of North Korea", and "the perfect stop off while en route to or returning from the Hermit Kingdom".

In an audio file posted on the website of the Terra Nova church in Surrey, British Columbia, and heard by AFP, Kevin Garratt tells the congregation: "We're China based, we're North Korea focused, but we're Jesus centred." "God said, in a prayer meeting, go to Dandong and I'll meet you there, and he said start a coffee house," he said in a guest sermon dated November last year.

"We serve the best coffee on the border... and we do some other things too.

"We're trying to reach North Korea with God, with Jesus, and practical assistance." North Koreans regularly stay at a "training house" outside Dandong, he said, and "99 per cent of the people we meet go back to North Korea, because they have to preach the gospel in North Korea, because God has compelled them to go".

The Canadian Embassy in Beijing said that it was aware of reports Canadians were being investigated.

"We are gathering information and monitoring developments closely," it said in an e-mail, but declined to release further information, citing privacy issues.

News of the investigation came just a week after Canada accused China of hacking into the computers of its research and development arm.

"Recently, the government of Canada, through the work of the Communications Security Establishment, detected and confirmed a cyber intrusion on the IT infrastructure of the National Research Council of Canada by a highly sophisticated Chinese state-sponsored actor," a government statement said last Tuesday.

Canada did not provide details on the nature of China's alleged cyber incident.

Beijing dismissed the claim as "groundless speculations and accusations" in a statement issued by its embassy in Ottawa.

Mr Garratt said that for now he and his two sisters and one brother are "confused" and "trying to get a handle on things".

His parents came to China in 1984, he said, and besides the coffee shop have engaged in activities including teaching English, running a consulting business, starting a kindergarten and helping Chinese orphans find homes in the West.

"Obviously, they've always had a huge passion for China and just helping the Chinese people in general and that's really been their goal everywhere in China they've been," he said.