Ankara, July 4 (IANS): Turkey's main opposition Republican People's Party (CHP) on Tuesday announced its appeal to the European Court of Human Rights over alleged irregularities in the April referendum on expanding the powers of the presidency.

"I should sadly state that the referendum has become illegitimate due to the decision by the Supreme Election Board," CHP leader Kemal Kilicdaroglu said as he continued a so-called Justice March with thousands of followers from Ankara to Istanbul.

"I am putting my first signature here now. The petitions will be sent today," Xinhua news agency quoted Kilicdaroglu as saying on the 20th day of the march in Kocaeli province.

The CHP failed in its bid for annulment of the April 16 referendum, in which constitutional amendments were passed by a slim majority to enable Turkey to switch to an executive presidency, though the opposition and international observers challenged the acceptance of unstamped ballots and other alleged frauds.

The Justice March was launched right after CHP lawmaker Enis Berberoglu was convicted and imprisoned by an Istanbul court on June 15 over espionage charges.