NMAC BTWN A B727 TURNING FINAL AND A BE35; XING UNDERNEATH TO FOLLOW ANOTHER B727 ON FINAL MISTAKEN FOR THE RPTR'S ACFT. SUBSEQUENT CONVERSATION WITH TWR REVEALED THAT THE TWR HAD CLRED THE BE35 TO FOLLOW RPTR AND THAT THE BE35 PLT HAD THE B727 IN SIGHT. HOWEVER; IT WAS THE WRONG ONE.

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CLRED THE SDF DME RWY 19 CIRCLE TO RWY 1 BEHIND AN ACR Y B727. ADVISED BY APCH AND TWR #2 BEHIND ACR Y. NO OTHER TA'S GIVEN TO US DURING THE APCH. JUST AS I WAS TURNING FINAL; DSNDING THROUGH 6300 FT MSL; TCASII ALERTED 'TFC' (NO TARGETS HAD PREVIOUSLY BEEN OBSERVED ON THE TCASII). A TARGET WITHOUT ALT INFO WAS CLOSE ENOUGH TO GIVE A TA ALERT. AT THE SAME TIME A LIGHT ACFT (BE35) WAS SEEN PASSING UNDER OUR NOSE 200-300 FT; R TO L. I ROLLED OUT TO ALLOW THE ACFT TO PASS TO OUR L; AND TO REMAIN CLR AND BEHIND THE OTHER ACFT. TWR WAS QUESTIONED AND ADVISED US THAT THE ACFT'S PLT HAD US IN SIGHT AND WAS FOLLOWING OUR ACFT. THE OTHER ACFT WAS NOW AHEAD AND TO OUR L. TWR ADVISED HIM SOMETHING IN SPANISH AND THEN ADVISED US THAT HE WAS DOING A 360 DEG TURN TO THE L AND FOR US TO CONTINUE TO RWY 1. AN UNEVENTFUL LNDG WAS MADE. PER A TELEPHONE CONVERSATION WITH TWR; I FOUND OUT THAT THE ACFT WAS A BE35. ALTHOUGH THE CONVERSATION WAS SOMEWHAT DIFFICULT DUE TO THE NORMAL LANGUAGE TROUBLES; I DETERMINED THAT THE TWR HAD ADVISED THE OTHER ACFT OF US (BUT NOT VICE VERSA) AND SINCE HE HAD CALLED US IN SIGHT AND WAS CLRED TO FOLLOW US; THEY WERE NOT CONCERNED ABOUT THE CLOSENESS. I BELIEVE THAT THE PLT HAD 'SPOTTED' ACR Y; ALSO A B727; AND WAS NOT AWARE OF US UNTIL WE QUESTIONED TWR ABOUT ANOTHER ACFT AND HIS INTENTIONS. BOTTOM LINE: EVEN IN RADAR AND COMS CONTACT IN A FOREIGN COUNTRY YOU MAY BE ON YOUR OWN!