The explosive device, fitted with a timer, was placed outside the restaurant in the southwestern province’s capital Quetta, local police chief Mir Zubair Mehmood said.
It was timed to explode late in the night when people had gathered on the eve of Pakistan’s 66th Independence Day being observed on Tuesday, he said.
“At least 12 people were injured, one of them is in serious condition,” Mehmood told AFP.
He blamed militants, saying “they wanted to create panic to disturb the national day celebrations”.
There was no claim of responsibility for the latest incident but the province which borders Iran and Afghanistan suffers from Taliban attacks.
It is also a flashpoint for sectarian violence involving Sunni and Shiite Muslims that has left thousands of people dead since the late 1980s.
Baluch rebels rose up in 2004, demanding political autonomy and a greater share of profits from the oil, gas and mineral resources in the region.
Bomb blasts and attacks on police and security forces are frequent in insurgency-plagued Baluchistan, which is one of the most deprived areas of Pakistan.