BEIJING (Reuters) -- Canadian Prime Minister Stephen Harper said Sunday he had raised concerns about China’s detention of a Canadian couple near the North Korean border during a meeting with Chinese President Xi Jinping. Kevin and Julia Garratt, longtime residents of China, have been detained since August for suspected theft of military and intelligence information and for threatening national security.

The couple’s son said earlier Sunday he was not sure Canada was doing enough to help his parents.

“That particular case is of significant concern to us, to Canadians, that’s why I raised it,” Harper told reporters after two days of bilateral meetings with China’s top leaders in Beijing. “We obviously want to have a good relationship, but it has to be a good relationship that serves this country’s [Canada’s] interests. And for that reason I raise issues where there are some significant difficulties between our governments, and I’m glad we’re able to have a frank exchange with Chinese leaders on those subjects.”

Simeon Garratt, the couple’s son, said he was reassured by Harper’s move to raise the case directly with Xi. “Everything that happened today was positive, we couldn’t really ask for much more. Concern has been expressed quite strongly, so I feel like we’re on the right track,” Garratt told Reuters in Beijing after Harper’s press conference.

While he had no idea when his parents, who operated a coffee shop near the sensitive North Korean border, will be released, he said he was optimistic it would happen. “Eventually I do. I can’t say exactly when, but I’m definitely positive this will be resolved at some point. It is just a matter of when,” he said.

Simeon Garratt’s visit to Beijing from his home in Vancouver coincides with Harper’s first visit to China in two years. Having met with Canadian consular officials in the Chinese capital, Garratt said he planned to travel Monday north to Dandong, near the North Korean border, to help sell his parents’ coffee shop and try to get a message to them.

Family members have not yet been able to visit the Garratts, who are being held separately, but Harper noted consular officials have been granted regular access.

Chinese Premier Li Keqiang also spoke about the case to reporters Saturday after a meeting with Harper. “As for the case, I want to reiterate that China is a country ruled by law, and is developing its legal institutions. The judicial authorities in China will handle the case in accordance with the law. At the same time the legal rights and interests of the people concerned will be protected,” Li said. “The governments of the two countries have also discussed and negotiated visits by consular officials,” he said.

Garratt said he was concerned about the health of his father. “Dad injured his leg quite badly from not being able to move and go outside,” he said. “I’m also worried about their mental health, being held in isolation, what effect that is going to have on them.”

The detention of the Garratts came less than a week after Canada accused Chinese hackers of breaking into a key computer network, the first time it has ever singled out China for such a security breach. Beijing dismissed the allegations as “irresponsible.”

(Reporting by Andrea Hopkins; Additional reporting by Megha Rajagopalan; Editing by Nick Macfie and Susan Fenton)