The boy died at the scene and the animal was later destroyed, police say.
A 10-year-old boy has died after being attacked by a dog, police have said.
The incident happened at about 16:00 GMT at a house in Pentwyn, Penyrheol, Caerphilly.
Paramedics from the Welsh Ambulance Service went to the scene where the boy was pronounced dead.
Gwent Police said the dog was destroyed by firearms officers and officers would remain in the area while an investigation is carried out.
One neighbour said the attack took place inside one of the houses on the street. He said he was shocked to hear what had happened.
The street is in the middle of a large housing estate and a few police vehicles remain parked at the end of the road on Monday night.
Earlier dozens of emergency service vehicles were on the scene.
Ch Supt Mark Hobrough said: “Officers will be making further enquiries at this time and will remain at the scene as the investigation progresses.
“It is possible that you may see ongoing police activity in Caerphilly as part of this work.”
He urged the public not to be alarmed adding: “If you have concerns or information then please do stop and talk with us.”
Caerphilly MS Hefin David said: “My thoughts tonight are with the families involved. I know the close knit community will rally round and offer support.”
Regional MS for South Wales East, Natasha Asghar added: “My heart goes out to this little boy and his family in Caerphilly who must be utterly devastated after what’s happened today.”