Are these attacks or bittorrent?

I am getting "Under SYN flood attack, sent TCP RST: TCP" and "syn
flood TCP" reports in my Zyxel router log. They are on the right
ports for BitTorrent and the NATted LAN address they're attempting to
go to does have BitTorrent running on it.

I was trying to see what was making the router active so I
disconnected everything (including the destination BitTorrent machine)
but the connections still continue.

Should I be worried and/or do something about it or is it just what
happens if you pull the plug on BitTorrent?

--
Chris Green