TikTok is hosting dozens of videos that glorify violence by Russia's Wagner Group of mercenaries and they have been viewed more than a billion times, according to a new report.
Wagner has sent mercenaries into Ukraine in big numbers.
US-based NewsGuard, which focuses on online misinformation, says some of the videos appear to show the execution of a former Russian mercenary.
TikTok has said it will act against any content violating its policies.
NewsGuard said it had identified 160 videos on the short-video platform that "allude to, show, or glorify acts of violence" by the mercenary group, founded by Yevgeny Prigozhin, a close ally of President Vladimir Putin.
Fourteen of those videos showed full or partial footage of the apparent killing of former Russian mercenary Yevgeny Nuzhin which saw high engagement within days of being uploaded last month, it said.
Analysts said one video of the murder was viewed at least 900,000 times before it was taken down. TikTok is owned by China-based firm ByteDance.
Nuzhin had been serving a jail term for murder but described how he had been recruited by Wagner and was then captured by the Ukrainian military. He told Ukrainian journalists he had switched sides voluntarily and denounced the mercenary group.
It is thought he was then part of a prisoner exchange and within days a gruesome video involving a sledgehammer was posted on a Wagner-linked channel on the Telegram messaging app.
NewsGuard found that TikTok's algorithm appeared to push users towards violent Wagner Group content.
When an analyst searched for the term "Wagner", TikTok's search bar suggested searches for "Wagner execution" and "Wagner sledgehammer". The same search in Russian resulted in the suggestions "Wagner PMC", "Wagner sledgehammer" and "Wagner orchestra". Wagner refers to its fighters as "musicians".
NewsGuard also found that videos could be found on TikTok showing another Wagner murder involving an army deserter in Syria in 2017 and that they had reached millions of users.
The online analysis group said it had also identified other music videos on the platform that advocated violence against Ukrainians, including calls to kill Ukrainians claiming they were "Nazis".
Responding to the report, a TikTok spokesperson said there was "no place for hateful or violent content on our platform". Many of the videos identified by NewsGuard were no longer available on the platform by Thursday.
"Our Community Guidelines clearly outline that we do not allow people to use our platform to threaten or incite violence, or share attacks or slurs based on people's nationality or other protected characteristics. We will take action on content found to violate these policies," TikTok said.
Wagner started out as a shadowy Russian mercenary group and in 2014 went to eastern Ukraine to help Russian proxy forces oust the Ukrainian military.
It has also been active in Syria and several African countries, and has repeatedly been accused of war crimes and human rights abuses. Last week the European Parliament called for it to be added to the EU's list of terrorist organisations.
This video can not be played
Watch: Russian mercenary group recruits detainees
For years Yevgeny Prigozhin denied he had anything to do with Wagner, until September when he finally admitted founding the group.
Once know as "Putin's chef" because of his catering fortune, he appeared in recent videos recruiting inmates in Russian prisons for the war in Ukraine.
Yevgeny Nuzhin's family knew nothing of his recruitment for the war, although before he died he told Ukrainian journalists he and the other prison recruits were merely "cannon fodder".
What is Russia's Wagner Group of mercenaries?
Wagner chief defends brutal killing video
Zelensky aide reveals up to 13,000 war dead
Wine, cheese and US-France diplomacy in Washington
New York and Singapore top most expensive cities
The new generation powering China's protests
Germany helps pay energy bills as prices soar
Weekly quiz: Which nation made Dua Lipa a citizen?
'I am very afraid', says Qatari transgender woman
India makes big strides in African healthcare
Damning report raises tough questions for SA leader
The mystery of the polar dinosaurs
Has the slap affected reviews of Will Smith's new film?
Is attacking Ukraine's power grid a war crime?
Is this the greatest taboo of all?
'I regret the role, not my daughter'
Artemis I: The giant rocket setting new records
© 2022 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.