Pompey fans have arrived at St Mary’s in the coach “bubble” for the derby clash with Saints.
Police say a group of Saints fans gathered at a working men’s club in Northam Road as the convoy of Pompey coaches went past.
Officers on horseback moved in to prevent any disorder.
A large group of Saints fans gathered at the police line on Britannia Road, shouting at the Portsmouth fans as they made their way into St Mary’s.
There was also a heavy police presence around Pompey fans, who were chanting and banging on windows, as they got off the coaches.
A window of one of the coaches was smashed.
Some Portsmouth fans were waving a banner that said: "We're being held against our will.
"Watching football is not a crime."
Police said all away fans were in the stadium by ten minutes before kick-off.
They said there was no "significant" intelligence of any planned violence but were prepared for any spontaneous pockets of disorder.
Both sets of fans have been warned violence at the game will not be tolerated and police will seek maximum football banning orders for anyone arrested.
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