Srimad Bhagavatam Canto 06, Chapter 12, Text 32

SB 6.12.32

bhittva vajrena tat-kuksim
 niskramya bala-bhid vibhuh
uccakarta sirah satror
 giri-srngam ivaujasa
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
With his thunderbolt, King Indra, who was also extremely powerful, pierced through Vrtrasura’s abdomen and came out. Indra, the killer of the demon Bala, then immediately cut off Vrtrasura’s head, which was as high as the peak of a mountain.
Srimad Bhagavatam Canto 06, Chapter 12, Text 31
Srimad Bhagavatam Canto 06, Chapter 12, Text 33