Okay, stupid question. But can you attack enemy ships when they are in a port (with your navy)?

I thought I did it a couple of turns ago but now I am not so sure as both the Shoni and Ouchi have fleets in their ports but when I go to attack them I only end up instigating a blockade of their ports (I've retried multiple times, and I'm definitely clicking on their navy and not their port). This is useless to me since their only trade routes are land based.

Seems dumb not to be able to attack them; makes me wonder if my savegame is corrupted.