A Russian diplomat accused of killing an Ottawa woman while driving drunk is using diplomatic immunity to avoid facing trial in Canada.

Andrey Knyazev the third-ranking Russian diplomat in Canada flew back to Moscow Monday after Russia refused Ottawa's request to waive his immunity.

50-year-old Catherine MacLean a prominent Ottawa lawyer was killed while walking her dog Saturday afternoon, after a car veered onto the sidewalk and struck her.

A woman walking with her was seriously injured and remains in hospital. The dog was also injured and had to be euthanized.

Police at the scene said the suspect refused to take a breathalyser and was so impaired he could barely walk or speak.

On Monday night mourners held a vigil in MacLean's memory, leaving flowers and candles in front of her house. Some called for changes to the immunity laws.

"It seems incredible to me that diplomats can come to another country and behave essentially with complete immunity from the most horrendous conduct," Janice Payne, a friend of MacLean's told CBC Newsworld.

Russia expressed deep regret over the accident, and added that sincere condolences have been passed on to the victim's family.

Two diplomats expelled

Knyazev is one of two Russian diplomats recalled Monday after being accused of drunk driving over the weekend. There were no injuries in the second incident.

The Canadian government had asked Russia to lift both men's diplomatic immunity so the suspects could be charged here. In denying the request, Moscow assured Ottawa the men will be charged in Russia.

In a statement, the Russian government said, "Upon an appropriate investigation in Moscow, the guilty will be called to account in accordance with the Russian legislation."

Canada's Chief of Protocol Richard Kohler says Ottawa only has the "moral power of persuasion" to convince Russia that the men should be tried in Canada. But he said Russian law is similar to Canada's when it comes to drunk driving.

Under the Vienna Convention, diplomats and their family members can be charged with crimes but are immune from criminal prosecution and civil liability. In some cases, they can be expelled from the country where they're posted.