ISLAMABAD — The Pakistani army entered the last of three militant strongholds targeted by a major offensive in the northwest on Friday, as gunmen wounded a senior army officer and a soldier in the capital.

The operation in South Waziristan, the main Taliban and al-Qaida sanctuary in Pakistan, has sparked a wave of retaliatory attacks that have killed about 300 civilians and security forces in the past month. The shooting in Islamabad was the third such attack in about two weeks.