Update: reportedly Malaysia Airlines has confirmed that plane "Kuala Lumpur -Amsterdam" went off the radar in Donetsk oblast, possibly shot down"

First it was MH-370. Now, it appears tragedy has struck again, this time on Malaysian Airlines flight MH-17, on route from Amsteram to Kuala Lumpur, which disappeared from radar moments ago and was reportedly shot down over Ukraine. While there is nothing yet officially confirmed by the carrier, the radar tracked path of the airplane is shown below.

And from a second source:

Last reported position log was at 1:20 pm UTC: