Carl Icahn has decided to fight a proxy battle with Yahoo and file a full board slate, Reuters is reporting, citing sources. The names could be announced as soon as tonight according to the report. Still not known: who’s with him and how Microsoft will respond to this. There’s a lot of balls in the air right now, but Icahn didn’t just spend $1 billion on Yahoo cause he’s a buy-and-hold kinda guy. Either way: the Yahoo story is back. Shares are moving up around $.60 after hours to about $27.70.

On Icahn’s objectives, WSJ has a different version from a source: Even without any certainty of an eventual Yahoo sale to Microsoft, Icahn considers its shares an attractive value and is willing to hold them for an extended period, it cites a source. We wondered about this possibility earlier, though even if it is an extended period, it won’t be a quiet, inactive one.

Meanwhile, Third Point, the hedge fund managed by once-venomous and famed activist investor Dan Loeb has disclosed holdings in both Yahoo and Microsoft (NSDQ: MSFT). The stakes aren’t large though: $194 million in Microsoft and $29 million in Yahoo (NSDQ: YHOO). It’s not exactly clear what the idea is, or when the shares were acquired: if this were just a play on Yahoo flipping to Microsoft, then it doesn’t make sense to buy more Microsoft than Yahoo. (via MarketWatch)

Update: WSJ: Icahn will nominate 10 candidates, including former Viacom (NYSE: VIA) CEO Frank Biondi. He’s hired proxy company D.F. King. “People close to the matter said Mr. Icahn failed to get a response from Microsoft about its interest in restarting acquisition talks.”

• Icahn Watch: Yahoo Shareholders Wait For The Next Move
• Updated: Icahn May Launch Yahoo Proxy Fight: Reports