Global Affairs Canada says it is closely monitoring a situation in Bangladesh involving a University of Toronto student detained by police for questioning after a deadly attack in a Dhaka café, but made no promises to help on Wednesday.

"There are limits to what any country can do for individuals who are not citizens of that country," Austin Jean, spokesman for Global Affairs Canada, said in a statement.

Jean said Canadian government officials abroad work under the guidelines of the Canadian Consular Services Charter. "The Privacy Act prevents us from sharing further details," he said.

Talha Khan, the older brother of Tahmid Khan and a Canadian citizen, said Wednesday he sent a lawyer's letter to Global Affairs Minister Stéphane Dion on Tuesday, asking him to provide consular assistance to his brother, who is a permanent resident of Canada but not a citizen.

Talha said his brother has epilepsy and that stress and lack of sleep can trigger seizures. He said the police questioning may be taking a toll on his brother and he is becoming anxious as the detention continues.

"We are optimistic that we will see him soon," Talha, a York University student, told CBC News. "My parents have faith in due process. But as a brother, thousands of miles away, I am a little anxious, and that's why I'm reaching out to the community."

Tahmid was detained on Saturday, immediately after authorities rescued him and 12 others from a Dhaka café. He was at Holey Artisan Bakery to meet two of his friends when armed attackers stormed the restaurant, holding hostages for nearly 11 hours. The attack killed 20 hostages and two police officers. ISIS has claimed responsibility.

Appeal for consular assistance

Marlys Edwardh, a lawyer with Goldblatt Partners in Toronto, who wrote the letter to Dion, said the minister has resources he can use to help Tahmid. "We're anxious that the government of Canada make inquiries and see if they can see him," she said.

"We have asked him to exercise his discretion as minister and take some steps to offer consular assistance, because indeed the circumstances, from our perspective, are worrisome. It is true that, while Talha is a Canadian citizen, his brother Tahmid is simply a permanent resident of Canada and that does not give Tahmid the same rights as a Canadian citizen has.

"He has yet to be sworn in as a Canadian citizen. That does not, however, exclude Canada from trying to provide consular assistance to someone who is detained in a foreign state. It really depends on whether the Bangladesh government will extend that courtesy."

Edwardh said a letter has also been sent to Nayem Uddin Ahmed, acting Bangladesh high commissioner in Ottawa, asking him to talk to the Bangladesh government to clear the way for Canadian consulate officials to provide assistance to Tahmid. She has been told that the commissioner is celebrating Eid for three days, starting on Wednesday, and will not respond until after that time.

No recent contact

Edwardh said the family wants reassurances that Tahmid is fine. "We believe he has seen no one and is in fact in detention without contact with the outside world," she said.

Talha said his parents are doing better than they were when Tahmid was being held hostage in Dhaka. "At one point we were not even expecting our brother and son back, so now we are in a better position than that."

He said he has received much support from friends in Toronto as the family waits for news. "I'm overwhelmed by the support that I've received from family and friends here," he said.

Tahmid is a fourth-year student at the University of Toronto. He was planning to complete a master's degree in public health. He applied for an internship with UNICEF in Nepal and was scheduled to leave Bangladesh on July 9 to go there. He was active in the Bangladeshi Student Association at the University of Toronto.