La Scala reopened in December after three years

The theatre's board sacked Carlo Fontana - who has headed the theatre since 1990 - citing "differences" with conductor Riccardo Muti.

La Scala reopened in December after three years, following renovations that cost an estimated 61m Euros (�42m).

In a statement, the theatre's board said it was "urgent to unify the theatre's management". Fontana has been replaced with Mauro Meli.

The sacking has prompted concern among La Scala staff .

Conductor Riccardo Muti is a powerful figure in the music world

On Thursday, protesting workers blocked a premiere of Tchaikovsky's opera The Queen of Spades, featuring leading Russian baritone Dmitri Hvorostovsky.

The La Scala board added it would "deal in a timely fashion" with the budget shortfall created by the renovations, with the aim of balancing La Scala's books in 2006.

The extensive renovation work, carried out amid fears that the venue would be ruined, was done to improve the theatre's acoustics and ability to stage productions.

The stage was entirely re-constructed, making it possible, in theory, to stage three different operas on the same day.

The heavy red carpets in the hall were also removed, reportedly improving the theatre's sound.

Tickets for the re-opening fetched up to 2,000 euros (�1,380)