India suspects that two senior leaders of a banned Pakistani militant group masterminded last week's three-day terrorist attacks that killed 171 people in Mumbai, an Indian intelligence official said Thursday. Evidence collected in the investigation of the deadly siege points to Zaki-ur-Rehman Lakhvi and Yusuf Muzammil, the official said, speaking on condition of anonymity because he wasn't authorized to speak publicly about the details. Lakhvi and Muzammil are believed to be top members of the outlawed Pakistani group Lashkar-e-Taiba, which India blames in the attacks. Muzammil is the group's chief of operations in Kashmir and other parts of India and Lakhvi its chief of operations, authorities said. The two suspects are believed to be in Pakistan , the Indian intelligence official said. Secretary of State Condoleezza Rice arrived in Pakistan on Thursday for meetings with civilian and military leaders after visiting Indian leaders in New Delhi. She aimed to raise pressure on Pakistan 's government to help get to the bottom of the terror attacks. The US wants Pakistan to do more to go after terror cells rooted in Pakistan . Joint Chiefs of Staff Chairman Mike Mullen was pushing the same message in Pakistan on Wednesday, and also was to meet with officials in India during his trip.