The device, which police have described as "significant" and "viable" has been taken away for forensic examination.
A 41-year-old man arrested on Thursday over dissident republican activity is still being questioned by police.
A quantity of cigarettes were also recovered during the searches.
Chief Superintendent Mark Burton said:
"The actions of police today have undoubtedly thwarted the attempts of criminals to inflict death, injury and misery on the people of north Belfast."