unicode safe alternative for fold

I'm using fold -w 3 to split a line into multiple 3 chars long, however with the GNU implementation, it does not work for text with multi-byte characters it seems. How can I achieve the above with sed? I've come up with sed -r 's/^(.{0,3})(.*)/\1\n\2/g' however this only does a single replacement: echo "111222333444555666" | sed -r 's/^(.{0,3})(.*)/\1\n\2/g' 111 222333444555666 --- Additional examples: echo "ĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄ" | sed -r 's/^(.{0,3})(.*)/\1\n\2/g' ĄĄĄ ĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄ And fold with it's corrupting behavior: echo "ĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄĄ" | fold -w 3 Ą� �Ą Ą� �Ą Ą�