ye ca dig-vijaye tasya
sannatim na yayur nrpah
prasahya ruddhas tenasann
ayute dve girivraje
Twenty thousand kings who had refused to submit absolutely to Jarasandha during his world conquest had been forcibly imprisoned by him in the fortress named Girivraja.
Srila Visvanatha Cakravarti points out that these kings refused the payment of tribute and other forms of submission to Jarasandha. Also, there is a well-known account in the Mahabharata and other literatures that Jarasandha desired to worship Maha-bhairava by offering him the lives of one hundred thousand kings in sacrifice.