The incident took place at a viewing center in the southern port city of Calabar.
Police spokeswoman Irene Ugbo told local media
victims died immediately when a high-tension electricity cable fell on top of the makeshift zinc house.
The fans congregated to watch the popular English team Manchester United play in a Europa League
quarter-final game against Anderlecht, a Belgian club.
There was initial confusion surrounding the number of deaths with some local media reporting that 30 fans had died.
Nigeria police later confirmed that seven fans passed away in the incident, with 10 seriously injured.
More than 80 people were at the center when the incident occurred around 9:48 p.m. Manchester United won the game 2-1. It was played at the Old Trafford stadium in Manchester.
"Our thoughts go out to the United fans, their friends and families affected by the tragedy in Calabar, Nigeria, yesterday," Manchester United said in a tweet.
Nigeria's President Muhammadu Buhari said he was "shocked and saddened" by the deaths.
In a statement, Buhari's aide Garba Shehu said: "The President commiserates with the government and people of Cross River State, and football fans nationwide over the unfortunate incident."