WikiLeaks has claimed in an editorial that it is being shadowed by elements of the US government.
The site's editor, Julian Assange, said that he was followed by two undercover state department officials on his way to Iceland to discuss the setting up of a journalist's safe haven within the country.
Assange also said that a WikiLeaks employee had been detained for 22 hours, and that computers had been seized by the authorities.
"WikiLeaks is currently under an aggressive US and Icelandic surveillance operation. Following, photographing, filming, detaining," WikiLeaks posted on Twitter.
The group added about an hour later: "If anything happens to us, you know why: it is our Apr 5 film. And you know who is responsible."
The date reference concerns a meeting WikiLeaks has arranged at the National Press Club where it is believed it will show footage of a bombing raid in Afghanistan from 7 May last year that left 97 civilians dead.
The tweets come barely a week after WikiLeaks uploaded a secret US Army report that classified the site as "a potential force protection, counter-intelligence, OPSEC, and INFOSEC threat to the US Army", and detailed plans to discredit the site.
“We have airline records of the State Dep/CIA tails. Don't think you can get away with it. You cannot. This is WikiLeaks," the tweets continued. "To those worrying about us – we're fine, and will issue a suitable riposte shortly."
Cotton seedling freezes to death as Chang'e-4 shuts down for the Moon's 14-day lunar night
Fortnite easily out-earns PUBG, Assassin's Creed Odyssey and Red Dead Redemption 2 in 2018
Meteor showers as a service will be visible for about 100 kilometres in all directions
Saturn's rings only formed in the past 100 million years, suggests analysis of Cassini space probe data
New findings contradict conventional belief that Saturn's rings were formed along with the planet about 4.5 billion years ago