* Investigations part of probe into Unipol-Fondiaria merger
* Unipol says it and managers acted properly, transparently
* Unipol shares down more than 7 pct (Adds Unipol statement, Consob)
MILAN, May 22 (Reuters) - The chief executive of Italian insurer Unipol has been placed under investigation for alleged market rigging in a case related to the company's merger with Fondiaria-SAI, two sources close to the investigation said on Thursday.
Unipol agreed to buy troubled rival Fondiaria in 2012 in a complex rescue operation that was held up by a series of regulatory and legal hurdles.
The merger created UnipolSai, Italy's No. 2 insurance group behind Assicurazioni Generali, and was officially completed on Jan. 6 this year.
Two sources familiar with the matter said Carlo Cimbri, who is chief executive of both Unipol and UnipolSai, was placed under investigation by Milan prosecutors in the probe.
In a statement Unipol, which controls UnipolSai, said that until Thursday it had received no request for information or clarification about the merger and denied any wrongdoing.
"The company now hopes for the conclusion of such investigations in a short time in the belief they will confirm the absolute correctness and transparency of the actions of the Unipol Group and of its representatives," it said.
Milan prosecutors are probing the Fondiaria group over a number of alleged irregularities by its previous owners and in the run-up to the merger.
They also suspect that Unipol did not accurately account for its large structured derivatives portfolio and that this had an impact on the setting of the share swap ratios for the tie-up with Fondiaria, according to judicial sources.
As part of the investigations the Italian tax police carried out searches at the headquarters of UnipolSai in Bologna on Thursday, a source said.
A spokesman for market regulator Consob said the police had also asked it for documents regarding the operation which it had promptly provided.
UnipolSai shares closed down 3.8 percent while Unipol shares ended the day down 7.3 percent. (Reporting by Manuela D'Alessandro; Writing by Stephen Jewkes; Editing by Paola Arosio, Tom Pfeiffer and Mark Potter)