MANILA, Oct 4 (Reuters) - A Philippine journalist has been shot dead while driving in the country's capital, police said on Tuesday, prompting condemnation from media groups and activists, who described his assassination as a blow to press freedom.Radio journalist Percival Mabasa, 63, was killed by two assailants at the gate of a residential compound in the Las Pinas area of Manila on Monday night, police said.Register now for FREE unlimited access to Reuters.comThe national police vowed to bring justice over the attack.President Ferdinand Marcos Jr's office was concerned about the killing and officials had been tasked to look at the conduct of the investigation, senior deputy executive secretary Hubert Guevara told reporters."We are not discounting the possibility that the shooting could be related to the victim's work in media," local police chief Jaime Santos said in a statement."