Romania's defence minister has said that remains of a drone used in a Russian attack on a Ukrainian port have been found on Romanian territory.
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His comments follow two days of him and other senior officials "categorically" denying any cross-border incident.
Ukraine had insisted it had evidence of the explosion.
Romania's president says the attack, which the defence ministry is investigating, would be a serious violation of Romania's sovereignty.
An attack on Romania, which is a member of Nato, would be "completely inadmissible", Klaus Iohannis said.
On Monday, Ukraine's foreign ministry had reported that Shahed drones "fell and detonated" in Romania on Sunday night after the latest Russian attack on the Ukrainian port of Izmail.
It called the incident further proof of the "huge threat" posed by Moscow to Ukraine's neighbours.
Now Romania's Defence Minister, Angel Tilvar, has visited the Danube Delta region close to the border with Ukraine and announced that several pieces of a drone had been found.
An investigation is now under way and the fragments are being analysed to determine whether they come from a Russian weapon.
Rebutting Kyiv's assertions became difficult after Ukraine's Foreign Minister Dmitro Kuleba announced publicly that he had photographic evidence of the incident.
He said it was "absolutely obvious" what had happened and that there was "no point in denying it".
The incident has brought angry reaction from Romanian commentators who want to know why the government denied an attack so quickly and unequivocally and suspect an attempted cover-up.
"It is because you still live with the mindset of 30 years ago, when nothing existed that the 'great ruler' did not want? Or was it just sheer stupidity?" defence analyst Andrei Luca Popescu asked, referring to the era of Communist rule.