<xsl:variable name="url">http://......svg...</xsl:variable>
<fo:block>
<fo:instream-foreign-object>
   <xsl:copy-of select="document($url)" />
</fo:instream-foreign-object>
</fo:block>

Hello again,

Sorry for replying to myself, but I'd like to add the following information:

I have just tried to add width and height attributes to fo:instream-foreign-object, and more space is reserved for the graphic, bue exactly the same portion is rendered.