© David Kawai/Bloomberg/Getty ImagesJustin Trudeau's tweet was taken down after 12 hours.
Celebrities and users shared a picture on Instagram showing a woman holding an Iranian flag with the caption "Iran sentences 15,000 protesters to death - as a 'hard lesson' for all rebels."
Instagram has since tagged the post as "False Information" and said "Independent fact-checkers say this information has no basis in fact."
The post, which has since been taken down, was shared by celebrities including actresses Sophie Turner and Viola Davis.
Trudeau tweeted late Monday that Canada denounces the "Iranian regime's barbaric decision to impose the death penalty on nearly 15,000 protestors." The tweet was up for 12 hours before being taken down.
"The post was informed by initial reporting that was incomplete and lacked necessary context. Because of that, it has since been deleted," a Canadian government spokesperson told CNN.
"It was based on reporting of serious concerns raised by international human rights advocates warning of possible future sentences, including the death penalty, imposed on thousands of Iranian protesters who have already been detained by the regime," the spokesperson added.
CNN has reached out to the Iranian Foreign Ministry for comment.
Iranian lawmakers are demanding that the country's judiciary "show no leniency" to protesters, but so far one person has officially been sentenced to death by the judiciary this week. However, the UN warned last week that others are at risk of receiving a similar sentence.
"With the continuous repression of protests, many more indictments on charges carrying the death penalty and death sentences might soon be issued," UN experts said last week.
"We should not lose sight of the fact that one person has already been sentenced to death, and that Iranian parliamentarians should not call for any death sentences to be imposed. Already, dozens of protesters have been killed by the regime's security forces," the Canadian government spokesperson said.
Iran has arrested more than 14,000 people in a crackdown since protests began across Iran in September, the UN Special Rapporteur on Human Rights in Iran, Javaid Rehman said earlier this month.
At least 2,000 people were charged for their alleged involvement in the nationwide protests over 22-year-old Mahsa Amini's death, the largest such show of dissent in years. The trials are public and have been underway for more than two weeks. The sentences can be appealed, according to state news agency IRNA.
At least 326 people were killed in the protests, human rights organizations said. CNN cannot independently verify arrest figures, death tolls, and many of the accounts of those killed, due to the Iranian government's suppression of the media, the internet and transparency.
Iran's Revolutionary Court issued the death sentence to the unnamed protester who allegedly set fire to a government building, state media said on Sunday. Five others who took part in the protests received sentences of five to 10 years in prison, convicted of "collusion to commit a crime against national security and disturbance of public peace and order."
The protests have sparked a fierce battle to control the narrative online, where supporters and opponents of the government alike are taking to social media to tell their version of the truth.
With access to Twitter blocked in Iran, that battle is primarily being fought outside the country.
And more and more people realize it.