Fake news has been widely circulating on Indian sites and social media this week, claiming a civil war had broken out in the Pakistani city of Karachi.
The reports emerged after local Pakistani media said troops had kidnapped the provincial police chief to force him to arrest a top opposition leader.
The story was quickly picked up over the border in Pakistan's arch-rival, India, where reports went much further - saying clashes between the police and the army had resulted in the deaths of many Karachi police officers and tanks had been seen on the streets.
A fake video circulating on Twitter even claimed to show some of the alleged unrest.
In reality, none of it was true.
Many local police and opposition members had been angered by events surrounding the politician's arrest - but there was no violence.
Pakistan and India are bitter enemies and it's well known they have long used propaganda against each other - they have fought three wars since independence from Britain in 1947.
Last year, Facebook blocked networks linked to Pakistan's military and a global network of pro-Indian fake websites and think-tanks was exposed, which had been aimed at influencing decision-making in Europe.
But what's notable this time is the number of verified accounts and apparently reputable news outlets that ended up putting out news that was utterly false, to millions of followers and readers.
'Fighting' in a place that doesn't exist
Tempers seemed to be simmering down when Pakistan's army chief ordered an investigation into the circumstances surrounding the arrest on Tuesday of Safdar Awan, the son-in-law of former Prime Minister Nawaz Sharif.
A day earlier there had been a major rally against the government of Pakistan's current Prime Minister Imran Khan in Karachi, an opposition stronghold which is the capital of Sindh province.
But later on Tuesday night a hitherto unknown account tweeted that a fight between troops and police had broken out, with tanks on the streets of Karachi and at least five casualties.
It's unclear who sent this initial tweet. Despite extensive digging by the BBC, it was not possible to establish who operates the Twitter account named @drapr007.
An hour later, the account tweeted again, this time saying: "#BREAKING: Heavy firefight between Pak Army and Sindh Police is going on in Gulshan e Bagh area of #Karachi..."
Those familiar with Karachi would know there is no area there by that name - but most readers would not.
Nor had there been any fighting, or tanks seen on the streets.
However, news of the "civil war" then spread rapidly. A deadly blast in Karachi which turned out to have been caused by a gas leak added fuel to the rumours.
They were picked up by verified individuals and major Indian media outlets such as CNN18, Zee News and India Today.
One user with a verified account, Prashant Patel - whose bio says is an advocate of the Supreme Court of India - went on to put out a series of tweets where he made claims about a "civil war situation" in Karachi, deaths of policemen and soldiers, Prime Minister Imran Khan ordering patriotic songs to be played on the radio, and even the impending arrival of the US Navy in the port of Karachi.
The BBC's Reality Check team looked into some of the accounts and websites - some of them impersonating the Sindh police - which have been spreading false news about the situation in Karachi and found them to have links with India.
Video purporting to show the clashes was shared by an account under the name of International Herald.
The dark and blurry video shows young men walking towards a building with fire visible to one side. They are seen throwing stones and shouting slogans, seemingly against Pakistan's army chief. The BBC was unable to tell if the video had been doctored, or even shot in Pakistan at all.
BREAKING : Civil war in Pakistan. Reported clashes between Karachi Police & Pak Army pic.twitter.com/tQsUWPx5pa— The International Herald (@TheIntlHerald) October 20, 2020
International Herald was registered under a now-defunct Indian company in 2018. It's had a Twitter account since 2015 which does not follow anyone. Its followers include two leaders of the ruling Bharatiya Janata Party (BJP) in India.
Mainstream Pakistani media outlets were quick to challenge the Indian media claims with fact-checks.
And Twitter users in Pakistan have had a field day ridiculing the reports, using hashtags such as "CivilwarKarachi", "fakenews" and "Indianmedia" trending on Twitter along with humorous posts and memes.
Renowned singer and actor Fakhr-e-Alam tweeted: "Karachi civil war has gotten so bad that my food panda delivery boy had to crawl through mine fields carrying his AK47, RPG & 9mm along with my nihari and Biryani. This thing is getting so serious."
Writer Bina Shah said: "I live in Karachi, where I just did my groceries, visited the bakery, bought some clothes and came home. If there's a civil war out there I couldn't find it."
Some called the reports a case of "co-ordinated disinformation" by Indian media.
If the ' news reports' originating in India re troops-police firefights etc in Karachi are an example of the 5th generation warfare we are constantly being warned of, we have nothing to worry about except whatever the consequences of laughing our heads off.— Abbas Nasir (@abbasnasir59) October 21, 2020
'So biased it does not make sense'
Hartosh Singh Bal, political editor of one of India's most respected news magazines The Caravan told the BBC: "There's a section of media in both countries which is essentially busy playing games, and what they do has little to do with journalism.
"It is so biased that it does not make sense."
Another senior Indian journalist who did not want to be named said projecting a divide between the army and police in Pakistan would fit into the Indian narrative of a Pakistan in decline.
"A quick study of Twitter handles tweeting this misinformation will show that most of them are supporters of or affiliated to the ruling party."
Arslan Khalid, who advises Imran Khan on digital strategy, said it was not the first time that Indian media had run a co-ordinated disinformation campaign against Pakistan.
He questioned Twitter's commitment to its guidelines.
Despite repeated attempts, the BBC was unable to obtain a response from Twitter regarding its policies on fake news.
The BBC's Reality Check and BBC Monitoring both contributed to this report.