Police official Mohammad Afzal said, "It was a bomb blast. It was inside the Islamic university building."
"There was another one a few minutes later," Afzal was quoted by a news agency referring to the Islamic International University, on Islamabad's eastern flank.
Reports said that at least four people have been killed and 18 others are injured in the twin blasts.
The injured have been rushed to the near by hospital, Afzal added.