DUP North Belfast MLA William Humphrey said those who placed a bomb in Belfast had committed a “criminal act of madness” which risked causing “carnage”.
The alert was announced at about 10am by police, who said roads in the Ainsworth Avenue area in the north-west of the city had been closed and homes evacuated.
An Army team confirmed the object, which Mr Humphrey said had been on a windowsill, as a “crude but viable device”.
Mr Humphrey said: “Whoever was responsible for this explosive device clearly cares nothing for the consequences of their actions.
“They were utterly reckless in placing the device on a windowsill beside the street in this densely populated area.
“The device has been described by the police as being a “crude but viable” bomb.
“It was left in a public area where a child or any passing person could have picked it up and there could have been carnage had it exploded.”