Ugandan police say they are investigating whether the killing of a prosecutor in Kampala late Monday was carried out by Somalia's Islamic extremist group al-Shabab.

Patrick Onyango, a police spokesman in the Ugandan capital, said Tuesday that Joan Kagezi, who had been a prosecutor in the ongoing trial of a dozen men facing terror charges, appears to have been the victim of a targeted assassination.

The U.S. Embassy in Uganda described Kagezi on Tuesday as a "heroine in the forefront of the fight against crime and terrorism."

Onyango said Kagezi was shot twice by gunmen after she left her car to buy groceries in a Kampala suburb.

The killing has shocked Uganda amid repeated warnings that al-Shabab, which carried out deadly bombings here in 2010, is plotting fresh attacks.