Dozens more are feared injured after the wire crashed into the supporters during United’s 2-1 win over Belgians Anderlecht in the Europa League
Police confirmed at least seven were killed but officials fear the toll could be far higher after the tragedy in Nigeria.
Ten more were confirmed to be critically injured.
The club this morning tweeted: "Our thoughts go out to the United fans, their friends and families affected by the tragedy in Calabar, Nigeria, yesterday."
A statement from football's governing body Fifa added: "Fifa is deeply saddened by the deaths of several football fans in Calabar & offer our deepest condolences to family & friends of the victims."
Journalists at the scene reported the death toll is likely to rise further.
While local Ukeme Joseph estimated at least 20 people had died after the wire collapsed onto the Calabar viewing centre where many Nigerians flock to watch Premier League teams.
As many as 80 supporters are believed to have been crammed inside the building.
State governor Ben Ayade, said: "It was heart-wrenching that the lives of the young men were lost through electrocution."
One local described how a transformer near the centre exploded sending the cable crashing down onto the fans.
The Manchester Evening News reported one witness as saying: "It happened during the match between Manchester United and Anderlecht.
"I heard a deafening bang. I rushed out to see what was happening.
“When I turned back to go inside the viewing centre, I saw a cable coming down on the centre and this electrocuted the viewers in the hall.
“It was a horrible sight to behold. I wish I didn’t come out to watch the match. Come to think of it, I have DStv at home but I enjoy watching matches at viewing centres.
"I could have been dead. I can’t believe that the people I was chatting and joking with a few minutes ago are all gone in a most anguishing way. This world is vain.”
Credit: The Sun