Security forces stepped up efforts across breakaway Chechnya on Saturday to find President Boris Yeltsin's kidnapped personal envoy to the Caucasus region.

Checkpoints were set up or reinforced at all main crossroads in the region, but police said the search had yielded no results so far and the whereabouts of Valentin Vlasov and his kidnappers were unknown.Chechen President Aslan Maskhadov told a news conference in the capital Grozny his administration would do its best to find and free Vlasov.

"We will spare no effort in finding Vlasov. We will also apologize to the Russian government and personally to Vlasov. The kidnapping happened on our territory and we bear the responsibility," Maskhadov said.

Maskhadov was expected to address the nation later on Saturday asking for help in finding and releasing Vlasov.

Chechen deputy premier Kazbek Makhashev said late on Friday that those involved in the incident had been detained, but he was referring to Vlasov's driver and bodyguard and not the armed men who snatched the envoy after stopping his car.

RIA news agency said prosecutors had issued a formal arrest warrant for the two on suspicion of involvement in the kidnapping.

Five gunmen fired shots and forced Vlasov's unescorted limousine to stop on the main Baku-Rostov road around noon on Friday, security officials said.

Vlasov is normally based outside Chechnya for safety reasons but travels to Grozny regularly for talks with Chechen leaders.

Ivan Rybkin, who co-chairs a Russia-Chechnya negotiations commission, said in televised remarks that he should not have been traveling without an escort vehicle. He said both sides had agreed on close cooperation in investigating the case.

But he ruled out paying a ransom and said he did not expect Vla-sov to be released soon.