SINGAPORE - While there has been "public disquiet" on the jail sentence of an American mixed martial arts instructor, who was jailed last Thursday (March 2), it is not an appropriate time to comment on the case, said Home Affairs and Law Minister K. Shanmugam.

This is because the time for an appeal to be filed is not over yet, he added.

"AGC (the Attorney-General's Chambers) makes the decisions based on precedents, and what kind of sentence is meted out depends on previous cases," he said.

"Having said that, my understanding is that AGC is looking into this," he added.

Mr Shanmugam was speaking on the sidelines of a fund-raising cycling event on Monday (March 6).

"I can understand that there is public disquiet on the sentence. People are naturally upset, parents in particular," he said.

Joshua Robinson, 39, had unprotected sex with two 15-year-old girls, filmed the acts with his mobile phone and showed an obscene clip to a third girl who was only six years old.

He also possessed 321 films containing child pornography with children as young as two years old - believed to be the largest number of such films seized from a single person in Singapore.

He was sentenced to four years' jail last week, a move that has attracted much public discussion.

In a public Facebook post last Friday that has since been taken down, the six-year-old's father expressed disappointment at Robinson's jail term, which he described as "a slap on the wrist".

An online petition against the sentence, started on Sunday night, has since attracted over 8,000 signatures.