The deployment on Tuesday is clearly aimed at bolstering the Italian contingent, left rattled by the blast that killed 19 of its members.
Nine Iraqis were also killed in the explosion that ripped through the Italian police headquarters in the city last Wednesday.
"We are well aware of the security problems but morale is good," a Portuguese commander Antonio Olivera said.
The Portuguese police, who have been assigned to many foreign missions in the past including Bosnia, East Timor and Kosovo, are under the command of the Italian Carabinieri police chief Burgio Carmelo.
"Its different here from Bosnia, the situation is worse with these suicide attacks," a member of the Portuguese contingent said.
The Portuguese deployment came as grieving Italians in Rome laid to rest the dead Italian policemen.
Members of the Italian contingent reiterated their resolve to carry on with their mission in Iraq.
"The tragedy has only changed one aspect of our work. We have more determination and more caution," Colonel Gian Franco said.
But amid the tough talking, there was more bad news for the occupation forces.
Ukrainian Defence Ministry said that one of its soldiers deployed in southeastern Iraq as part of the US-led occupation force had shot and killed himself.
No reasons were given as to why he took his own life.
The soldier was part of the 1650 Ukrainian contingent deployed in the Iraqi province of Wasit since August.