A Saudi Arabian organisation has apologised for tweeting a digitally altered image that showed a plane flying towards Toronto’s CN Tower – in an apparent reference to a 9/11-style attack – amid an escalating row over Canada’s call for the release of detained human rights activists in the kingdom.

Infographic KSA, a pro-government Saudi Twitter account, shared the image on Monday, hours after Riyadh announced it had expelled the Canadian ambassador and suspended new trade and investment with Ottawa.

Counting several Saudi diplomatic figures among its more than 350,000 followers, the now-deleted account is run by volunteers and managed by Saudi youth with an interest in technology and social media, according to an affiliated website.

The row appeared to worsen on Wednesday when the Saudi Press Agency reported that Saudi Arabia had halted all treatment programs in Canada and was arranging the transfer of all Saudi patients from Canadian hospitals to other hospitals outside the country.

The image, which showed an Air Canada plane aimed at Toronto’s skyline, attracted criticism soon after it was posted. Some saw the image as a veiled reference to the 9/11 attacks on the US, in which 2,996 people were killed after 19 hijackers flew airliners into the World Trade Center’s twin towers and the Pentagon. Fifteen of the hijackers were Saudi nationals.

A screenshot of the now-deleted tweet Infographic KSA posted on Monday. Photograph: Twitter

Captions on the image spoke of “sticking one’s nose where it doesn’t belong”, while another warned: “He who interferes with what doesn’t concern him finds what doesn’t please him.”

The post was retweeted hundreds of times before Infographic KSA deleted it and apologised. “The aircraft was intended to symbolize the return of the ambassador,” the organisation said in a subsequent tweet. “We realize this was not clear and any other meaning was unintentional.”

Soon after, the Saudi ministry of media said it had shut down the account amid an investigation into a complaint over it.

The post comes during a high-profile spat that began when Global Affairs Canada expressed its “grave concern” over the imprisonment of human rights activists in Saudi Arabia.

Riyadh shot back, lashing out at what it described as “a blatant interference in the Kingdom’s domestic affairs, against basic international norms and all international protocols”.

On Sunday, the Saudi foreign ministry said it had given the Canadian ambassador 24 hours to leave the country and recalled its own ambassador to Canada. The country’s education ministry is reportedly looking to move thousands of Saudi scholarship students out of Canadian schools, while Saudi Arabia’s state airline said it would suspend flights to and from Toronto.

Analysts described Saudi Arabia’s actions as a broader message to the world and an effort to demarcate the limits of reforms ushered in by the 32-year-old crown prince, Mohammed bin Salman. While he has sought to introduce social and economic change to the ultraconservative kingdom, he has not eased the absolute monarchy’s total ban on political activism.

On Monday, Canada’s foreign minister, Chrystia Freeland, said her government – which has come under fire previously for signing off on the sale of more than 900 armoured vehicles to Riyadh – would not back down. “I will say Canada is very comfortable with our position,” she told reporters. “We are always going to speak up for human rights, we’re always going to speak up for women’s rights, and that is not going to change.”