A group of Russian human rights activists wants the government to open a new investigation into the 1999 apartment bombings that killed about 300 people.

In an open letter, the activists say the bombings brought on a period of "official propaganda and lies" and created "unceasing terrorist threats" from rebels in the North Caucasus.  

Twelve leading veteran activists published the letter Thursday on a Web site frequently critical of the Kremlin, www.grani.ru.

The Kremlin blamed the September 1999 blasts in Moscow and two other cities on Chechen separatists. The attacks led to Russia's second military invasion of Chechnya in less than a decade.

The letter says the Kremlin's unwillingness to carry out what it calls a real investigation of the bombings has added to suspicions that the country's security services were involved.

Some observers claim Russian security services orchestrated the bombings to justify military intervention in Chechnya and help Vladimir Putin rise to power.

Mr. Putin was prime minister at the time of the bombings. He became Russia's acting president when Boris Yeltsin stepped down as president at the end of 1999. About 20 people gathered Thursday in Moscow to demand that authorities open a new investigation into the bombings.

Some information for this report was provided by AP.