You can setup your own entry by:
\newcommand{\addtocentrylistof}[3]{%
\ifstr{#2}{}{%
\addcontentsline{lof}{#1}{#3}%
\addcontentsline{lot}{#1}{#3}%
}{%
\addcontentsline{lof}{#1}{\protect\numberline{#2}#3}%
\addcontentsline{lot}{#1}{\protect\numberline{#2}#3}%
}%
}
\renewcommand*{\addparttocentry}[2]{%
\addtocentrydefault{part}{#1}{#2}%
\addtocentrylistof{part}{#1}{#2}%
}
Here a small example:
\documentclass[english]{scrreprt}
\usepackage{babel}
\newcommand{\addtocentrylistof}[3]{%
\ifstr{#2}{}{%
\addcontentsline{lof}{#1}{#3}%
\addcontentsline{lot}{#1}{#3}%
}{%
\addcontentsline{lof}{#1}{\protect\numberline{#2}#3}%
\addcontentsline{lot}{#1}{\protect\numberline{#2}#3}%
}%
}
\renewcommand*{\addparttocentry}[2]{%
\addtocentrydefault{part}{#1}{#2}%
\addtocentrylistof{part}{#1}{#2}%
}
\def\examplefig{\begin{figure}[!ht]\caption{foo}\end{figure}\begin{table}[!ht]\caption{foo}\end{table}}
\begin{document}
\tableofcontents
\listoffigures
\listoftables
\part{O I}
\chapter{foo}
\examplefig\examplefig\examplefig
\chapter{foo}
\examplefig\examplefig\examplefig
\chapter{foo}
\examplefig\examplefig\examplefig
\part{O II}
\chapter{bar}
\examplefig\examplefig\examplefig
\chapter{bar}
\examplefig\examplefig\examplefig
\chapter{bar}
\examplefig\examplefig\examplefig
\end{document}