"I believe it is the handiwork of groups who are trying to spread terror in our country," Sriprakash Jaiswal, junior home minister, said.
But Padam Kriti, spokesman of the state's Bar Association, said that this year the state's lawyers had decided not to defend suspects held on "terror" charges.
He said "it looks like" that decision may have been behind the blasts.
Carnage
Nine people were killed, including three lawyers, in the Hindu holy city of Varanasi and four more people died in Faizabad, according to JN Chamber, the Uttar Pradesh home secretary.
He said three blasts were reported from Varanasi and two each in Lucknow and Faizabad.
Vipin Mishra, a spokesman for the home ministry, said the blasts in Varanasi killed two lawyers and injured at least 12 others.
The blasts went off less than 15 minutes apart inside court complexes, but not in courtrooms, Mishra said.
NDTV news channel showed what appeared to be at least one dead man lying on a pavement, with other wounded people were lying nearby.
Lucknow is the capital of Uttar Pradesh and Varanasi is a popular Hindu pilgrimage centre.
At least 15 people were killed and 60 wounded there in three explosions in 2006.