A two-year-old girl has become the second child in the US to be shot dead by a sibling this week, after her five-year-old brother shot her with a rifle designed for children, officials revealed on Wednesday.

Officials in Kentucky say the five-year-old boy was playing with a rifle designed for children and given to him as a gift, when he accidentally shot his younger sister.

The two-year-old girl was pronounced dead after being rushed to a hospital following the shooting on Tuesday in rural Kentucky, police said.

The death follows a similar incident on Monday where a five-year-old girl in a remote Alaska community was reportedly shot and killed by her eight-year-old brother.

Cumberland County coroner Gary White identified the two-year-old Kentucky girl as Caroline Starks and said the children's mother was cleaning the house at the time and had stepped outside onto the porch.

"She said no more than three minutes had went by and she actually heard the rifle go off. She ran back in and found the little girl," Mr White said.

The .22 calibre rifle had been given to the boy last year and was kept in the corner of a room. The parents did not realise a shell had been left in it.

"It's a Crickett," Mr White told the Lexington Herald-Leader. "It's a little rifle for a kid ... the little boy's used to shooting the little gun."

The Crickett is just one of many child-sized rifles on the market and is sold with the tag line 'My First Rifle'.

It comes in a number of child-friendly barrel designs and colours, including hot pink for little girls.

A host of accessories are also available, like story books and a gun-toting beanie baby of the rifle's mascot, a cartoonish cricket.

An autopsy was set to be conducted but Mr White said he expects the shooting will be ruled accidental.

"Just one of those crazy accidents," Mr White said.

Gun control debate

The US has been embroiled in a heated debate over gun control and gun culture in the wake of a horrific December shooting at a school in Newtown, Connecticut that killed 26 young children and educators.

US president Barack Obama has pushed for tougher federal gun laws that require universal background checks on gun buyers and called for a ban on assault weapons like the one used in Newtown.

But last month, his background check proposal - condemned by the powerful National Rifle Association as an infringement on Americans' constitutional right "to keep and bear arms" - failed to muster the necessary 60 votes needed to clear the US Senate.

There were 851 deaths caused by accidental discharges of firearms in the US in 2011, according to the latest data from the Centres for Disease Control and Prevention.

A further 14,675 people were injured by accidental discharges of firearms in 2011, of whom 7,991 were under the age of 18 and 3,569 were under the age of 13.

No efforts have been made to prevent children from using firearms for hunting and sporting purposes, a treasured tradition for many American families.

AFP