President Volodymyr Zelensky called on Wednesday for Ukraine's allies to share "all the data" held on the missile that landed in Poland, which Kyiv insists was fired by Russia, a claim contradicted by Warsaw.
Two people were killed on Tuesday when at least one missile hit the village of Przewodow near the Ukrainian border, during a mass Russian bombardment aimed at civilian infrastructure inside Western-backed Ukraine.
In the immediate aftermath of the incident there were fears it could mark a new escalation in the conflict, but by Wednesday Poland announced the projectile likely originated from Ukraine's own air defences. That theory was then endorsed by Washington.
"We want to establish all the details, each fact. That's why we need… access to all the data that our partners have and the site of the explosion," Zelensky said in his nightly address.
Zelensky had earlier said Kyiv had not seen proof that the missile was Ukrainian and that it was imperative that Kyiv become part of an investigation.