One explosion late on Monday damaged a government building in Bhairahawa city, about 280km southwest of the capital, Kathmandu, and another hit a city council office in nearby Butwal, said a government official.
Two more blasts hit near a police station in Pokhara, a resort town about 200km west of Kathmandu, a police officer in Pokhara said. No casualties were reported.
No one immediately claimed responsibility, but the explosions came hours after Maoist rebels announced that they planned to resume attacks.
The rebels began fighting in 1996 to replace the constitutional monarchy with a socialist state. The insurgency has claimed about 12,000 lives.
But they declared a three-month unilateral ceasefire on 3 September, which they later extended by a month, offering a chance for peace.
On Monday, hours before the ceasefire was set to expire, the rebels announced that they would not be renewing it because the government had refused to match their pledge. Prachanda said government troops attacked rebel positions throughout the Maoists' ceasefire.
Under the ceasefire, the rebels pledged not to attack military or civilian targets to promote a return to peace talks, but they continued to block highways, extort money and kidnap villagers for indoctrination sessions.