Six-year-old twin boys and two adults were in the house at Glenpark Court in the Oldpark area when the attackers struck shortly after 0200 GMT on Thursday.

The device was put into the letterbox, causing blast damage to the front door and hallway of the house.

The walls have been damaged and the ceiling and the front door but it could have been worse Terri Fegan Mother of twins

The loyalist paramilitary Red Hand Defenders has said it carried out the attack.

The Red Hand Defenders is a cover name which has been used in the past by the Ulster Defence Association and Loyalist Volunteer Force.

The property is in a nationalist area on the edge of Ardoyne but the police have said it is too early to say why the family was targeted.

The children's mother said they were so frightened that they locked themselves in their bedroom.

"There was panicking and shouting and even today they are complaining of sore legs and they're still a bit shaky and tired," said Terri Fegan.

"The walls have been damaged and the ceiling and the front door but it could have been worse - it could have been the kids lives or my own life.

"It's only a door and that so we're lucky in that way."

Bombs defused

Several hours earlier six pipe bombs were made safe by Army bomb experts in north Belfast.

The alarm was raised on Wednesday when the six devices were discovered in the front garden of a house at Glenburn Park.

The security forces were called to the scene and the street was cordoned off.

Bomb experts moved in to examine the suspicious objects and determined they were viable explosive devices.

A number of follow up searches were carried out but nothing was found.

Police are investigating how the devices came to be in the garden.

Both incidents are not thought to be linked at this stage.