The damaged lines were repaired by 6pm and traffic was restored by 6:30pm on the track where only two trains including Chilton and Khushhal Express operate.
Meanwhile, troops escaped possible losses when two rockets targeting a key garrison in Quetta failed to explode after their timers malfunctioned, police said.
"We got information that two rockets fitted with timers had been placed on the western bypass in the suburbs of Quetta," city police chief Pervez Rafi Bhatti told AFP.
"Luckily the timers did not work, otherwise the rockets could have caused damage in the cantonment area," Bhatti said.
Security agencies and police have increased their patrols after the incident, he said.
Nobody has claimed responsibility for the failed attack, Bhatti said.
Those attacking government and military installations would be "sorted out", he said, alluding to the little known nationalist group, the Baloch Liberation Army, which had claimed responsibility for several similar attacks in the past.