\documentclass{book}
\usepackage[utf8]{inputenc}
\usepackage[sectionbib,numbers]{natbib}

\begin{document}

\chapter{CHAP 1}

\section{SEC 1.1}

\def\bibsection{\subsection*{Section Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\section{SEC 1.2}

\def\bibsection{\subsection*{Section Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\def\bibsection{\section*{Chapter Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\chapter{CHAP 2}

\section{SEC 2.1}

\def\bibsection{\subsection{Section Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\section{SEC 2.2}

\def\bibsection{\subsection{Section Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\def\bibsection{\section{Chapter Bibliography}}
\begin{thebibliography}{12}
\bibitem{bib1} Bla
\end{thebibliography}

\end{document}