By Andrew Harding in Moscow

It has been a week of intrigue and mystery in Moscow.

Almost every day Russian prosecutors, backed up by police commandos, have raided another prominent company in the city.

In each case, the firm involved is alleged to be linked to Boris Berezovsky, a powerful, manipulative tycoon with close ties to President Yeltsin's family.

The prosecutors say they are looking for evidence of multi-million dollar fraud and illegal surveillance.

The national airline, Aeroflot, is among the companies being targeted.

At a major oil company, Sibneft, investigators say they found equipment used to record the telephone conversations of some of Mr Yeltsin's relatives.

Russian politicians and commentators seem convinced that the prime minister, Yevgeny Primakov, is behind the crackdown.

They say he is trying to weaken if not crush Mr Berezovsky - a man once believed to have the power to make and break governments.

It is not clear where President Yeltsin himself stands.

Twice this week he has rushed to the Kremlin unexpectedly, despite the fact that he is still recovering from a bleeding stomach ulcer.

On the first trip he accepted the resignation of Russia's prosecutor general, Yuri Skuratov.

Officially, the 47-year-old Mr Skuratov quit because of heart problems, but few believe that.

Instead his departure has been linked by some to the growing scandal surrounding Mr Berezovsky, whose influence over one of Russia's main television channels is also being challenged.

Typically, the whole affair remains shrouded in secrecy and awash with speculation.