The former partner of siege gunman Man Haron Monis will be taken into custody after her bail was revoked by a Sydney court.

Amirah Droudis is facing murder charges over the death of Monis' former de facto Noleen Hayson Pal, who was stabbed and set alight in April 2013.

Droudis had been granted bail in December but today this was revoked at Downing Centre Local Court.

Monis was on bail when he took 18 people hostage inside a popular CBD cafe last week in a siege that ended with his death and that of two hostages.