There were 61 cases of assault within the prison walls last year, 21 of which were attacks on prison staff by inmates.

But compared to other countries like the United Kingdom, where there are more than 40 violent incidents within their prisons daily, the number here is low.

This was revealed by the Singapore Prison Service (SPS) in a statement on Friday, shortly after one of its officers, Lim Kwo Yin, 36, was fined $10,000 for causing the death of an inmate by negligence.

The inmate, Dinesh Raman Chinnaiah, 21, had kicked a prison warden before he had to be restrained in the incident that led to his death in Sep 2010.

There are about 12,000 inmates in the custody of the SPS, many of whom are serving sentences for violent crimes, said the prison service.

"Acts of indiscipline and violence, though not high, are not uncommon," added a prison service spokesman. "In 2012, there were 61 assaults by inmates, 40 of which were against other inmates and 21 against prison staff."