GROZNY, July 20 (RIA Novosti) - A lawyer for Chechen President Ramzan Kadyrov has begun legal action against the head of a human-rights group, Oleg Orlov, for slander, a presidential spokesman said on Monday.

Lawyer Andrei Krasnenkov has submitted to the Moscow Interior Department a request for a defamation case to be launched against Orlov, who accused Kadyrov of involvement in the murder of human-rights activist Natalya Estemirova.

In a statement published on Memorial's website last Wednesday, Orlov said: "I know, I am certain who is to blame for the murder of Natasha Estemirova. We all know this person. His name is Ramzan Kadyrov, the president of the Chechen Republic."

Estemirova, who had been investigating kidnappings and disappearances in Chechnya for Memorial, was abducted and murdered last Wednesday in the south Russian republic.

Kadyrov's press service said last Friday the Chechen leader had called Orlov, and said: "You are not a prosecutor or a judge, and so your statements about my guilt are, to put it mildly, unethical and insulting to me."

Russian President Dmitry Medvedev has dismissed claims that Kadyrov was behind the murder as "primitive."

Orlov earlier said "It's good that Ramzan Kadyrov has decided to deal with a conflict using legal methods. You have to take responsibility for your words and I am ready to do so in court."

Meanwhile, Kadyrov ordered on Monday the Interior Ministry to complete the investigation into the murder as soon as possible and to find and arrest those guilty.