Two German police officers shot dead during a traffic check
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The shooting happened at around 4:20 am (0320 GMT) in the Kusel district of western Rhineland-Palatinate state during a routine patrol.
A 24-year-old female police officer and her 29-year-old male colleague were killed.
The young woman was still in police training, according to Rhineland-Palatinate Interior Minister Roger Lewentz.
"We are urgently searching for the fugitive perpetrators," Westpfalz regional police said in a statement.
"At least one of the suspects is armed," they warned, urging residents not to pick up hitchhikers.
The shooting occurred on a small country road surrounded by forests and fields, a regional police spokesman told Welt TV.
The two officers managed to report that shots had been fired but radio contact was lost shortly afterwards, he said.
Backup police then arrived at the scene and found one officer dead and the other fatally injured.
The police said they had no description of the assailants' vehicle and did not know the direction in which the suspects had fled.
Kaiserslautern city police said they had extended their search area to the neighbouring state of Saarland, near the borders with France and Luxembourg.
"Please do not pick up any hitchhikers in the Kusel district!" they tweeted.
"My thoughts are with the families, friends and colleagues of the victims. We will do everything possible to apprehend the perpetrators," she said.
Police said the motive for the shooting remained unknown.
Germany's Bild newspaper quoted unnamed sources as saying the two officers had pulled over a "suspicious vehicle" and radioed in to say they had found dead game in the trunk, before shots were fired.
The female police officer's gun was found still in its holster, according to Bild, suggesting she had not had time to open fire.
Her colleague managed to draw his weapon before being killed, Bild added.
Germany's GdP police union expressed its "deep shock and sadness" over the shooting.
"Our thoughts are with the relatives and loved ones of the colleagues who died as a result of an act of violence in the line of duty," GdP deputy chief Joerg Radek said.