How to put logo at the top (header side) of title page in beamer (theme warsaw)?

I want to put 2 logos at the header of title page as illustrated in figure, any idea please?

\documentclass{beamer}

\usetheme{Warsaw}
\makeatletter
{
\leavevmode%
\hbox{%
\begin{beamercolorbox}[wd=.5\paperwidth,ht=2pc,left]{}
\colorbox{green}{\hbox to 5pc{\vbox to 2pc{}}}
\end{beamercolorbox}}%
\begin{beamercolorbox}[wd=.5\paperwidth,ht=2pc,right]{}
\colorbox{red}{\hbox to 5pc{\vbox to 2pc{}}}
\end{beamercolorbox}%
\vskip0pt%
}

\makeatother
\begin{document}
\section{Section}
\subsection{Subsection}
\begin{frame}
\frametitle{Frame title}
\end{frame}
\end{document}


Here you can change \colorbox{green}{\hbox to 5pc{\vbox to 2pc{}}} and \colorbox{red}{\hbox to 5pc{\vbox to 2pc{}}} with \includegraphics{...}. Also you can change the height by changing ht=2pc.