Gunmen killed Peru's naval attache to Bolivia on a downtown street Tuesday, and a previously unknown extremist group claimed responsibility in a note left near his body, witnesses said.

A man and a woman grabbed Capt. Juan Vega Llona one block away from the Peruvian Embassy, and one of them fired three shots at his head, witnesses reported. Vega Llona died instantly.The man and the woman immediately left the site and have not been found, the Ministry of the Interior said.

Police mobilized units throughout La Paz in a effort to capture the killers.