Imprisoned Saudi blogger Raif Badawi has been on a hunger strike since Tuesday after being transferred to a "new isolated" prison, his wife said on Thursday, according to the Reuters news agency.
Haidar, who lives in Canada where she and their three children were granted political asylum, confirmed the news by phone after tweeting it.
Badawi is serving a 10-year sentence after being convicted of insulting Islam and breaking Saudi Arabia's technology laws with his liberal blog. He also was sentenced to 1,000 lashes, spread over 20 instalments, and fined $266,000.
In June, Saudi Arabia's supreme court upheld the sentence against Badawi, who ran a website called Free Saudi Liberals and has been in custody since 2012.
Western governments have condemned Badawi's treatment, and rights groups including Amnesty International have campaigned for his release. Swedish Foreign Minister Margot Wallstrom accused Saudi Arabia of handing a "medieval" punishment to Badawi.
Colette Lelievre, a Montreal-based campaign organizer with Amnesty International, told Reuters on Thursday the group had been told Badawi was transferred to a different prison for "administrative reasons." Amnesty had not yet independently confirmed he started a hunger strike.
Canadian Foreign Minister Stephane Dion told reporters in Ottawa that the federal government was still seeking confirmation that he had changed prisons.
"We are very concerned about the situation of Mr. Badawi," he said, according to Reuters. Asked if Canada was making representations to the Saudi embassy, he replied, "We are doing our best to make sure that we will have a positive result in the end."
Haidar will be traveling to France to accept the prestigious Sakharov Prize awarded to her husband during a ceremony in Strasbourg on December 16, Lelievre said.