KIEV, Ukraine (AP) _ Ukraine's presidential candidates placed blame on each other and the president Monday for a grenade attack that injured a top contender and dozens of other people.

Police have arrested two suspects in the apparent attempt Saturday to assassinate radical leftist legislator Natalia Vitrenko during an election meeting in southeastern Ukraine.

Vitrenko, a popular challenger to President Leonid Kuchma, escaped with superficial injuries. At least 33 others, mostly members of Vitrenko's Progressive Socialist Party, were wounded.

Police quoted one suspect as saying he received the grenades from his brother, a campaign organizer for another candidate, Socialist Party head Oleksandr Moroz.

Security officials said Monday they were searching for the campaign organizer, who could have escaped into neighboring Russia.

Moroz angrily denied any connection to the attack, describing it as a ``preconceived, planned and organized provocation'' designed to ``implement the plans of the present regime to introduce state of emergency and thwart the elections at any cost.''

He said the alleged provocation was directed against the so-called ``Kanev Four'' group of candidates formed ahead of the Oct. 31 presidential ballot, Ukrainian media reported.

The group includes Moroz, centrist former Prime Minister Yevhen Marchuk, parliament speaker Oleksandr Tkachenko and another candidate. They have promised to unite behind a single contender, and Moroz appears to stand the best chance.

Kuchma is seeking re-election and is engaged in a serious battle with the leftists. The left-wingers accuse Kuchma of adopting a failed course that has only aggravated Ukraine's post-Soviet economic and social decline.

Tkachenko alleged in a statement that the assault ``should be linked to the work of the current president's election headquarters, and not to Moroz,'' the daily Kievskie Vedomosti said.

Kuchma did not directly comment on his opponents' allegations. He said Monday the attack was well planned and had clearly been ordered by someone.

``The question is, whose order it was,'' he said. ``This act was aimed at aggravating the social and political situation and derailing the presidential election.''

Several candidates said the attack would boost the rating of Vitrenko, who has been running second to Kuchma in recent polls.

Oleksandr Baziliuk, a marginal contender, told Kievskie Vedomosti in an interview published Monday that ``any candidate would benefit from a failed assassination attempt which only scratched a fingertip.''