The forced eviction last Thursday of squatters running the Ungdomhuset, or "Youth House", sparked nights of violent protests. The centre had been a haven for the city's youth and its underground culture since 1982.
Consulate staff in Venice said around 40 members of an Italian youth group sent a message from their office to the Danish government demanding the release of the activists that have been detained.
The Venice protest ended peacefully with no arrests.
|"The situation is a lot calmer. But we are maintaining our presence in the streets at the same high level"|
Flemming Steen Munch, Copenhagen police spokesman
Around 50 members of two other youth groups staged a similar protest at the Danish consulate in Milan shortly afterwards.
Italy has many "social centres" - buildings occupied, often illegally, usually by left-wing groups which use the space as a meeting place or to hold concerts.
Protests spilled over to Norway on Monday. Around 150 demonstrators gathered at the Danish embassy in Oslo to protest the demolition, throwing stones and paint before police fired tear gas to disperse them.
One policeman was hurt in the clashes in Norway but no arrests were made according to public broadcaster NRK.
Around 50 activists briefly occupied the Danish consulate in Bergen, using a computer there to print out a statement, before leaving when police arrived, local media reports said
Vandals also hit the Danish consulate in Kristiansand on the south coast with graffiti, Norwegian news agency NTB reported.
In 2001 the youth centre building was sold to the Christian group Fadershuset, which requested the eviction of the youths.
An August 2006 court ruling ordered the eviction of the youths, who insist the building belongs to them.
Around 675 people - including 60 minors - have been arrested since the disturbances erupted in the Noerrebro and Christianshavn neighbourhoods of Copenhagen following the evictions.
Rioters hurled petrol bombs and stones during three nights of disturbances.
On Tuesday, 190 remained in custody, according to police. Among those arrested were some 145 foreigners, mainly Germans and Scandinavians suspected of involvement in the disturbances.