Prostitutes working along the EN125 between Fontainhas in Albufeira and Boliqueime have been advised by the GNR not to frequent the area for safety reasons following a spate of robberies.
On May 14, a prostitute in her 20s was a victim of an armed robbery while she was in a car with a client.
Two men threatened the pair with a gun before stealing the woman’s earnings and the man’s wallet.
A GNR spokesman said: “The PJ are investigating the armed robbery.”