The United Nations nuclear watchdog says it has found no sign of undeclared nuclear activity at three sites in Ukraine that it inspected at the country’s request in response to Russian allegations that work was being done on a “dirty bomb”.

Russia has repeatedly accused Ukraine of planning to use such a bomb – a conventional explosive device laced with radioactive material – and said institutes linked to the nuclear industry were involved in preparations, without presenting evidence.

Ukraine’s government denies the accusation.

Some Ukrainian officials have accused Russia of making the allegation to give itself cover to detonate its own dirty bomb and pin the blame on Ukraine.

The International Atomic Energy Agency said last month it would inspect two locations in Ukraine following a request by officials in Kyiv.

On Monday it said those inspections had begun and on Thursday it said they had been completed at three locations rather than two, all of which had been mentioned by Russia.

“Over the past few days, the inspectors were able to carry out all activities that the IAEA had planned to conduct and were given unfettered access to the locations,” the Vienna-based IAEA said in a statement.

“Based on the evaluation of the results available to date and the information provided by Ukraine, the agency did not find any indications of undeclared nuclear activities and materials at the locations.”

The IAEA named the locations as the Institute for Nuclear Research in Kyiv, Eastern Mining and Processing Plant in Zhovti Kody and Production Association Pivdennyi Machine-Building Plant in Dnipro.

Inspectors also took environmental samples that will be sent off for lab analysis and the IAEA will report back on the results, the statement added.