A string of attacks involving the Crown Heights Jewish and black communities has prompted an increased police presence.The NYPD patrolled Eastern Parkway with a mobile crime unit Wednesday while other officers stood watch outside the main synagogue in Crown Heights. In addition, a watchtower was set up on the corner of Carroll Street. Commissioner Ray Kelly made a surprise visit to the neighborhood Monday to address the security issues. ?I think it will help somewhat but the bottom line is we need to deal with the racial conflict behind it all,? says Crown Heights resident David Johnson.The increase in security came after hundreds of members of the Jewish community marched demanding increased protection. The recent area violence included attacks on a black man and another against a Jewish teen.RayKelly meets with Jewish leaders about attacks