Sharif emerged victorious in the country's elections last weekend.
"We want to congratulate Nawaz Sharif and the people of Pakistan who showed tremendous courage in turning out to cast their votes despite threats to their life. But we remain very concerned about the violence in the run up to the election day and reports that in some districts women were prevented from voting.
"All these incidents must be thoroughly investigated by the authorities and the new government as soon as it is formed," Mustafa Qadri, Amnesty International's Pakistan Researcher, said here.
Four blasts had rocked Karachi as people voted, killing 14 people and wounding dozens. Across the country, at least 29 people were reportedly killed in election day violence on May 11.
However, despite the pre-election attacks, voters lined up at polling stations nationwide to ensure the first transition between civilian governments in the nation's 65-year history.