Comedian Robin Williams has sparked fears for his health after cancelling a string of stand-up performances, citing shortness of breath. The 57-year-old actor is under observation from doctors and has been ordered to rest for a week after the scare.

The star was scheduled to perform his one-man comedy show Weapons of Self-Destruction at various venues across Florida this week (begs02Mar09) but cancelled the gigs to recuperate. The four axed shows will be rescheduled and Williams hopes to continue his 80-city comedy tour on 8 March with a show in Jacksonville, Florida.