What does "whom" refer to in this sentence?

Nik   Mon Jun 11, 2007 8:42 am GMT
Supporters are urging him to take action against the demonstrators, several of whom are members of the parliament.
Does "whom" in this sentence refer to "supporters" or "demonstrators"? If it refers to "supporters", do you think this is a good sentence?
Guest   Mon Jun 11, 2007 9:08 am GMT
The demonstrators.
Guest   Mon Jun 11, 2007 9:32 am GMT
If it were referring to the supporters, it would be "Supporters, several of whom are members of the parliament, are urging him to take action against the demonstrators."