Each year Iranians celebrate Chaharshanbeh-Soori, an ancient Zoroastrian tradition on the eve of the last Wednesday of the Iranian calendar, by jumping over bonfires.
But fireworks and improvised explosives are also used to mark the event, often causing casualties.
Among the three who died on Tuesday night was a 45-year-old man who suffered a heart attack brought about by an explosion, said Amin Saberinia, head of Iran’s Emergency Medical Service.
The other two were a 24-year-old man and a teenager, Saberinia told the official IRNA news agency.
Some of the injuries were serious, including of a 14-year-old boy who lost both hands and was in a coma, Saberinia said.
The youngest victim was a three-year-old girl who lost fingers. Most of the injured — 234 out of 259 — were men.
Many Iranian actors, artists and celebrities this year urged people to stick to the traditional fire-jumping and refrain from using fireworks ahead of Nowruz (New Year), which starts on March 20.
Some did heed the advice and Saberinia said the number of injuries were about 50 percent lower than last year, when three people were also killed.
The death toll has been falling in recent years, with nine killed in 2014 and 19 in 2013.
Many Iranians have taken to staying indoors for fear of being hurt on Chaharshanbeh-Soori, when blasts and whistling explosives ring out across Tehran.