You can define subfigures:

<div id="fig:subfigures" class="subfigures">

+-----------------------+-----------------------+-----------------------+
| ![a](fig1.png){#fig:s | ![b](fig2.png){#fig:s | ![c](fig3.png){width= |
| ubfig1                | ubfig2                | "100%"}               |
| width="100%"}         | width="100%"}         |                       |
+-----------------------+-----------------------+-----------------------+
| ![d](fig4.png){#fig:s | ![e](fig5.png){width= | ![f](fig6.png){#fig:s |
| ubfig4                | "100%"}               | ubfig6                |
| width="100%"}         |                       | width="100%"}         |
+-----------------------+-----------------------+-----------------------+
| ![g](fig7.png){#fig:s | ![h](fig8.png){width= | ![i](fig9.png){#fig:s |
| ubfig7                | "100%"}               | ubfig9                |
| width="100%"}         |                       | width="100%"}         |
+-----------------------+-----------------------+-----------------------+

Figure 1: Caption. a — 1, b — 2, c — 3, d — 4, e — 5, f — 6, g — 7, h —
8, i — 9

</div>

<div id="fig:subfigures2" class="subfigures">

+-------------------------------------------------------------------------+
| ![a](fig1.png){#fig:subfig21 width="100%"}                              |
+-------------------------------------------------------------------------+
| ![b](fig2.png){#fig:subfig22 width="100%"}                              |
+-------------------------------------------------------------------------+
| ![c](fig3.png){width="100%"}                                            |
+-------------------------------------------------------------------------+
| ![d](fig4.png){#fig:subfig24 width="100%"}                              |
+-------------------------------------------------------------------------+
| ![e](fig5.png){width="100%"}                                            |
+-------------------------------------------------------------------------+
| ![f](fig6.png){#fig:subfig26 width="100%"}                              |
+-------------------------------------------------------------------------+
| ![g](fig7.png){#fig:subfig27 width="100%"}                              |
+-------------------------------------------------------------------------+
| ![h](fig8.png){width="100%"}                                            |
+-------------------------------------------------------------------------+
| ![i](fig9.png){#fig:subfig29 width="100%"}                              |
+-------------------------------------------------------------------------+

Figure 2: Caption. a — 1, b — 2, c — 3, d — 4, e — 5, f — 6, g — 7, h —
8, i — 9

</div>

Figures themselves can be referenced fig. 2, as well as individual
subfigures: figs. 1 (a), 1 (b), 2 (i)