Regulators said on Friday they were reviewing the safety of Allergan Inc's Botox and a competing product after reports of deaths and serious reactions in some patients.

The Food and Drug Administration said the most serious cases included hospitalizations and deaths and occurred mostly in children treated for cerebral palsy-associated limb spasticity, a use not approved in the United States.

The FDA said its review applied to Allergan's Botox and Botox Cosmetic, and Solstice Neurosciences Inc's Myobloc.