Local media say among the fatalities, three victims drowned, one died in a road accident and two others died during a fight among revelers.
Kyodo news agency says hundreds of thousands of people participated in the annual Buddhist New Year festival known as Thingyan.
Burma's military government warned party-goers to not wear provocative clothing and to not say anything that could damage national unity.
More than 300 persons died during a similar water festival in neighboring Thailand.
Information for this report is provided by AP and AFP