A number of suspicious attacks have taken place during the conflict leading to questions being asked about them.
What is a false flag event?
A false flag event is when a military or political action takes place by one side with the aim of blaming it on their opponent.
This is often done by the staging of a real or fake event against their own side in order to put responsibility on another.
The term dates back to the 16th century when pirates would fly the flag of a friendly nation in order to mislead a ship, allowing them to get close without causing concern.
In military terms a false flag is carried out in order to give reason to an action, such as an invasion.
Why are Russia being accused of them?
The US believe Russia could launch a chemical attack after the Russian Defence Ministry accused Ukraine of preparing a false flag chemical weapons operation.
“We do believe that we should be on the lookout for Russia to possibly use chemical or biological weapons,” a US official said.
If such an event took place Russia would feel they have the justification to launch chemical weapon attacks of their own.
The Ukraine Ministry of Defence say they have intelligence the Russians are preparing a terrorist attack at the Chernobyl nuclear station which they can blame on Ukrainians.
Russia claimed on Wednesday, but have offered no proof, that Ukrainians in the city of Zolochiv brought in more than 80 tons of ammonia and are training locals how to react after a chemical attack.
There were other claims of falsehoods from Russia, as they said a woman photographed injured outside a children's hospital in Mariupol was a 'crisis actor'. A tweet making the claims sent by the Russian embassy in the UK was blocked by Twitter whilst the woman in question, fashion blogger Marianna Podgurskaya, was later pictured having given birth to her baby.
Where have 'false flags' been used before?
Germany's invasion of Poland, 1939
Seven German soldiers pretending to be Polish stormed a radio station in Gleiwitz, Germany, to broadcast a short message saying they had taken control of the station.
A civilian's body was left behind at the building dressed as a Polish soldier to further exaggerate the ruse.
Adolf Hitler then gave a speech to justify the invasion of Poland, citing the Gleiwitz attack, among others, as the reasons behind it, ultimately starting World War II.
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Both Pakistan and India have accused one another of creating false flag events in an attempt to provoke the other with regards to the disputed border.
Pakistan accused India of firing on UN observers on the Pakistani side of the border with the aim of giving the UN the impression they were to blame.
The theory was that it would cause tension between Pakistan and the international community.
Pakistan's Prime Minister Imran Khan criticised the move, describing it as "reckless".