An explosive device has been found outside the home of a brother of murdered solicitor Pat Finucane, Sinn Féin said.
Martin Finucane is also the uncle of the party's MP John Finucane.
Army technical officers examined the object in the front garden of the house in west Belfast and declared it to be the remnants of a crude bomb which did not ignite.
Shortly after 6.30am it was reported that it had been thrown at the front window of the house, causing the outer pane of glass to smash, police said.
Sinn Féin MP Paul Maskey said: "A crude explosive device has been left outside the west Belfast home of a brother of murdered solicitor Pat Finucane early this morning.
"This is wrong and I unreservedly condemn it.
"This attack is reckless and shows a callous disregard for the Finucane family and the local community.
"This is an attack on a justice and human rights campaigner and as such is an attack on the whole community.
Those behind this device have nothing to offer society."
He urged anyone with information on the attack in Glenties Drive to take it to police.
Two adults who were in the house at the time were not injured, officers said.
PSNI Detective Sergeant Keith Wilson said: "A motive for this attack has not yet been established.
"We are extremely fortunate no one was injured in what was a reckless act in a built-up area."
He confirmed military experts had found the object to be the remnants of a crude explosive device that did not ignite.
Pat Finucane, 39, was shot dead at his north Belfast home in front of his family by loyalists in 1989.
Campaign group Relatives For Justice said it was "absolutely sickened that a bomb has been thrown at the home of one of our founding members".
It added: "Martin has travelled the world to shine light on state collusion, in his brother's case and hundreds of others. Our solidarity is with him this morning."
The Pat Finucane Centre, a campaign and advocacy organisation, said it was "shocked" at the attack on one of its board members.