Here is an excerpt from an interview with the head of Hamas Sheikh Yassin( [link|http://www.salon.com/news/feature/2001/08/10/yassin/index.html|http://www.salon.co...n/index.html] ):
Q. The relationship between Hamas and the Palestinian Authority has improved a lot with the Intifada. What kind of contacts do you have with Arafat?
A. I had an hour long face-to-face meeting with Arafat a month ago.

If the head of Hamas can meet with Arafat the Arafat is responsible at least in part for his actions.