Adding Tcl source to an R package

Dear R Community,

I'm writing an R package with a lot of Tcl and Tk code. I use the Tcl
wrapper functions provided by the tcltk package if possible. However I
also define "pure" Tcl functions. I so far defined them with the .Tcl
function, for example (in R):

.Tcl('proc test {a b} {
?return [expr {sqrt(pow($a,2)+pow($b,2))}]
}')

so that I can use the procedures later on with either

.Tcl('test 2 3')
or
tcl('test',2,3)

My Question: Where can I put my procedures in a *.tcl file within my
package structure and how do I make my R package to load the Tcl
procedures? And will these functions be within a Tcl namespace?