Ukraine's Interior Ministry has begun searching for Dutch paintings stolen back in 2005, Foreign Minister Pavlo Klimkin reveals.

"The Dutch side raised the issue during the visit of the Ukrainian President to [the] Netherlands. Our Ministry of Interior is working on this," Klimkin told reporters when asked the question by Interfax on Tuesday.

Western media reported earlier on the alleged involvement of the former chief of the Ukrainian Security Service (SBU) Valentyn Nalyvaichenko and leader of the Svoboda all-Ukrainian union Oleh Tiahnybok in the ransom demands with respect to the paintings previously stolen from a museum in Netherlands.

Klimkin claimed that some actions by the museum had hindered the search.

"The museum started the negotiations itself. There is no information about how it conducted the talks. Now, both the Interior Ministry and the Dutch Embassy [are] engaged in this. I hope that our coordinated efforts will lead to a success," Klimkin said.

This incident "is very important for those attempting to spoil our image, which is critical ahead of the referendum due on April 6," Klimkin said. "And we are just trying to arrange the logical concept and strategy for our further actions. Most of the steps have been agreed upon; we know how we are going to act in the short term. But the paintings issue is crucial for our image in many aspects," he said.

"I hope that it will have no impact [on the results of the Dutch referendum on the Ukraine-EU association] and we will demonstrate the success [of the investigation] before the referendum starts. And everybody will understand how it should be done: not by initiating some uncontrolled negotiations with God knows whom and publicly disclosing this information, but by working in contact, the contact between law enforcement officers of the two countries. The way it is going on now, after the Dutch side briefly raised this issue during our president's visit to Holland," Klimkin said.

The Ukrainian online newspaper Europeiska Pravda reported earlier, citing NOS, that Arthur Brand representing the West Friesland Museum claimed that a collection, composed of 24 paintings, stolen in 2005 was held by a OUN (Organization of Ukrainian Nationalists) battalion that attempted to trade these pieces of art for EUR 50 million. The battalion has connections "[at] the very top political level", Brand says. Employees of the museum also said that Tiahnybok and Nalyvaichenko could be implicated in this story.

Meanwhile, Nalyvaichenko categorically denies the statements of the Dutch side about his alleged complicity in the ransom demands.