Here is the account of the killing of Shalva from a 24,000 shloka Bharata samhita (reconstructed by me)
Krishna said "O tiger among the Bharatas! I had gone to Saubha, the city of Shalva. Listen to the reason why I went there. O best among men! The illustrious and mighty-armed king, the heroic Shishupala, son of Damaghosa, was slain by me. O best of the Bharatas! At your Rajasuya sacrifice, on account of the honour that was bestowed there, that wicked man, overcome by rage, could not endure it. When Shalva heard that he had been slain, he was filled with intense anger. O Bharata! While I was away, he came to Dvaraka when it was left unprotected. Then that evil-minded one slew many of the young Vrsni heroes and laid waste all the royal gardens.
He cried out “'Where is that disgrace to the Vrishni race? Where has that foolish Vasudeva, the son of Vasudeva, gone ? I shall crush the pride of that man who seeks battle with me. Tell me truthfully, O people of Anarta, where he has gone. After slaying that destroyer of Kamsa and Kesin, I shall return. By truth I swear, laying my hand upon my weapons, that I shall not return without killing him.
Today I shall send that sinner, that base betrayer of trust, to the abode of Yama, out of wrath for the slaying of Shishupala. Through the wickedness of that evil-natured man, my brother, King Shishupala, has been slain. I shall kill him upon the earth. He slew my brother, a youthful king, not in the forefront of battle. That hero was killed while off guard. I shall slay Janardana!”
O Kaurava! I heard all that had been done by that wicked king of Marttikavata against me. Then, O Kaurava, my eyes reddened with anger, and I resolved in my heart that he must be slain. I reflected upon the devastation wrought in Anarta, the insult done to me, and the swelling arrogance of that evildoer.
Then, O king, I sounded my conch Panchajanya and summoned Shalva to battle. For a long while I fought there against him and the Danavas. I subdued them all and cast them down upon the earth. O mighty-armed one! It was because of this undertaking that I could not come there at that time. Only afterwards did I hear about the game of dice at Hastinapura, born of unrighteous conduct."
- 15, Kairata Parva, Mahabharata.
Note - I have not included the Shlokas 6, 11, 15 and 19 which shows Saubha as a flying city.
The detailed multi-chapter long ‘Saubhopakhyana’ would not have been part of the 24,000 shloka Bharata Samhita.