The Gaza Strip has seen more clashes a day after Palestinian leader Mahmoud Abbas called for early elections to end an economic and security crisis.

Mortars were fired at Mr Abbas's office in Gaza City, and a 19-year-old woman was killed as rival Fatah and Hamas supporters clashed in the streets. A Hamas minister's convoy was attacked, as was a presidential guard base.

Prime Minister Ismail Haniya, who heads a Hamas-led government, has said new elections could incite further unrest. "The Palestinian government rejects the call for holding early parliamentary elections because it is not constitutional and may lead to a large disturbance in the Palestinian territory," said Mr Haniya.

Could someone explain this to me? I thought that one of the advantages of parliamentary style government was that you could call early elections. How does the Palestinian system work? I'm asking about the mechanics of the political system.