The curfew was imposed early on Sunday morning after protesters took to the streets of Quetta, the provincial capital, on hearing of the death Nawab Akbar Khan Bugti, 79, late on Saturday.
Bugti died in one of the biggest battles in years in Pakistan's gas-rich Baluchistan province, where Baluch nationalists have long demanded a bigger share of government spending.
Demonstrators burned more than a dozen vehicles, three banks and a petrol station, residents said.
There were no reports of any casualties in the protests but about 100 people, most of them students, were arrested, police said.
"We've imposed a curfew at 6am (0100 GMT). All shops are closed and the army have been called and they're taking positions," said Zahid Afaq, a senior Quetta police official.
"At the moment, the curfew is only in Quetta, but if there is any law and order situation elsewhere, it will be imposed there too."
Baluchistan is Pakistan's biggest but poorest province. It also has Pakistan's main natural gas reserves.
Men look on as a bus burns
during unrest in Quetta
Baluch separatists have long complained that the province does not get a fair share of the profits from its resources and they have been agitating for autonomy for years.
Government officials involved with security said more than 20 members of the security forces and nearly 40 rebels had been killed in the fighting in which Bugti was killed.
The military only confirmed the death of four officers and one soldier in the fighting on Saturday, in the province's Kohlu district.