A high-level prosecutor on Tuesday began an investigation into recent press speculation of stock manipulation on the Athens Stock Exchange, linked with last week's merger proposal by National Bank with rival Alpha Bank.

Chief prosecutor Yiannis Sakelakos ordered a preliminary investigation into the trading of stocks of the two banks.

The Capital Market Commission also ordered an investigation into the same affair, focusing on the time period of Feb. 8 to 21, beginning with National Bank's first approach to Alpha for a takeover via confidential discussions. Indeed, according to the Commission, the price of Alpha shares and National Bank rose by 33 percent and 18 percent, respectively.

The investigation was assigned to prosecutor Isidoros Dogiakos, whose orders include the investigation of possible use of insider information, a misdemeanor, unless the benefit arising for whatever perpetrators is more than 100,000 euros, which renders the offense a felony.