16:30GMT: WikiLeaks reported on Twitter: "We are currently under a mass distributed denial of service attack."
The Guardian's David Leigh noted that "The #guardian will publish US embassy #cables tonight, even if #wikileaks goes down"
16:48GMT: WikiLeaks update: "El Pais, Le Monde, Spiegel, Guardian & NYT will publish many US embassy cables tonight, even if WikiLeaks goes down"
17:07GMT: El País on Twitter: @wikileaks: pese al ataque a su web. El Pais, Le Monde, Speigel, Guardian & NYT publicarán los papeles que desnudan la diplomacia de EEUU
17:52GMT: WikiLeaks.org appears to be back up.