Before cheering armed loyalists outside the Bab al-Aziya compound, he claimed the capital Tripoli was under the control of pro-Kadhafi forces.
"I am here to refute the lies," the 39-year-old told journalists smiling broadly and flashing the V for victory sign. "Everyone should rest assured. All is well in Tripoli." Seif claimed the rebels had suffered heavy casualties on Monday when they attempted to storm the compound.
On Monday, International Criminal Court prosecutor Luis Moreno-Ocampo claimed Seif had been arrested and called for his swift transfer to The Hague to face charges of crimes against humanity.
Meanwhile, on the ground, the battle for Tripoli continues. On Sunday, jubilant rebel forces packed in trucks and cars streamed across the city seizing control of Kadhafi's state television network and the capital's seaside Green Square, renaming it Martyrs Square.
But there are signs that the rebels advance is faltering.
Gunfire is still heard around the city, but loyalist snipers are hiding on rooftops and the rebels have so far been unable to capture Kadhafi's compound. The whereabouts of Kadhafi are unknown although the US says there is no indication that he has left Tripoli.
Rebel chief Mustafa Abdel Jalil claims the "Kadhafi era is over", but conceded the rebels did not have complete control of the city and the "real moment of victory" would be when Kadhafi was captured.
The rebels claim to have cut off a column of pro-Kadhafi troops attempting to march on Tripoli from the city of Sirte, the leader's hometown.
But the rebels, whose supply lines are very thinly spread, acknowledge they cannot advance until thousands of reinforcements arrive from around Libya.