He said the explosion in the capital killed one person, although the Uganda Police chief political commissar Asan Kasingye said late on Saturday that two people were killed.
At least seven people were injured, TV station NTV reported.
"It seems to be a terrorist act," Museveni Tweeted on Sunday.
"The information I have is that 3 people came and left a package in kaveera [plastic bag] which later on exploded," Museveni said.
There was no immediate claim of responsibility, Reuters reports.
Officials did not immediately respond to requests for comment.
The blast occurred at Digida Pork Joint, a restaurant, local media reported.
Videos shared on social media showed panicked and confused revellers illuminated by blue police lights.
Bomb blasts in the East African country are rare. Kampala suffered a major attack by Somalia's al Shabaab in 2010 that killed dozens. The group said it had attacked Uganda as a punishment for its deployment of troops in Somalia.
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