A boy is being treated in hospital after being bitten in the head by a dog, believed to be an XL bully.
The eight-year-old was attacked in a communal area of flats near Wadham Road, Bootle at about 17:20 GMT on Saturday, Merseyside Police said.
He was taken to hospital where he is in a stable but serious condition.
A 49-year-old woman and a 30-year-old man, who are not related to the child, have been arrested, while the dog has been seized by police.
The pair were detained on suspicion of being a person in charge of a dog dangerously out of control and causing injury.
They have been taken into police custody for interviews.
Officers said they had spoken to witnesses and appealed for anyone with information to contact them.
Det Insp Gary Stratton, from Merseyside Police, said: “I want to reassure people that [the boy] is receiving the best possible care and treatment for his injuries, which are described as life-changing