Regular expressions - problem to replace multyline html tag

[Plato2]

I'm using regular expressions to replace a multyline hyperlink:
result_str = Regex.Replace(result_str, "<a[^>]*>(.*?)</a>", "", RegexOptions.Multiline)

This expression replaces all hiperlinks except for multyline hyperlink
The following hyperlink was not replaced
<a href="site2.dtw/disp?lotnbr=10825334&pix=C">
<img
src="/photo_i.jpg" name="full2"
></a>
How can I replace this kind of hyperlink with empty string?

Thanks in advance