MOSCOW (AP) _ President Boris Yeltsin dissolved the Security Ministry and created a new internal security unit today, saying the successor to the KGB had proved to be ''unreformable.''

Yeltsin's decree was his first major move in response to the defeat of reformers at the hands of ultranationalists in parliamentary elections Dec. 12. The ministry had been blamed for not warning Yeltsin of the voter support for extremist leader Vladimir Zhirinovsky.

Earlier today, in his first public comment on Zhirinovsky's victory, Yeltsin declared the strong showing by extreme nationalists a ''protest against poverty,'' and ordered Moscow officials today to pay more attention to the poor.

Yeltsin's long silence about the elections has left many wondering whether his commitment to reform is wavering. His brief remarks did not clarify whether he plans to proceed full speed with reforms or slow them down. His Cabinet is reportedly divided on the issue.

It was not immediately clear how the new security body would differ from its predecessor. The head of the dissolved agency, Nikolai Golushko, was named to head the new one, the Federal Service of Counterintelligence.

''At the present time there is a lack of a strategic concept for the state security of the Russian Federation and the Ministry of Security ... Counterintelligence activity was weakened,'' Yeltsin's decree said.

After the failed coup by Communist hard-liners in August 1991, the KGB was split into foreign and domestic units. The Security Ministry was responsible for counterintelligence and internal security.

The Security Ministry had been in turmoil for months and some of its members joined hard-liners who occupied the Russian parliament after it was dissolved by Yeltsin on Sept. 21.

Yeltsin earlier this year fired Security Minister Viktor Barannikov, who later went over to the side of the hard-liners and is now awaiting trial for his role in the October violence.

''Attempts in the last several years to forcibly reorganize (the ministry) were of an outward, cosmetic character,'' Yeltsin's decree said.

Some shakeup of Yeltsin's government had been expected following the disastrous loss of the reformers in the elections, but the changes had been expected to involve those responsible for economic reforms.

The dissolution of the Security Ministry might be an indication that Yeltsin was extremely angry about the way some parts of his government handled the October political violence and subsequent elections.

All employees of the Security Ministry will be forced to be cleared again before they will be permanently taken on by the new counterintelligence organization.