Bandaranaike is a member of a political dynasty going back 50 years and was already a cabinet minister, the BBC reported Monday. Both parents of the president and her brother served as prime minister.
The new foreign minister will keep his current position of tourism minister, while turning over his Industry and Investment Ministry responsibilities to Finance Minister Sarath Amunugama. He previously served as parliament speaker as well.
The Tamil Tiger rebels, blamed by the government for Kadirgamar's Aug. 13 assassination, have denied any involvement in the killing. The assassination of Kadirgamar, an ethnic Tamil strongly opposed to the Tigers, has thrown into doubt the country's cease-fire -- in effect since February 2002.
In response to the killing, the government introduced emergency rule, allowing the deployment of troops throughout the country.
The Tigers have been fighting for a separate nation for the minority Tamils in the north and east since 1983. More recently disputes over the administration of tsunami relief efforts and the sharing of international aid have caused tension.