GLOBAL MARKETS-Shares pummelled, dollar slumps as rout gathers pace

* Nikkei plummets more than 6 pct, European shares fall 1.3 pct * Dollar slides to 10-week low vs yen, 3-1/2 month trough vs euro * Fed tapering uncertainty stirs liquidations by funds By Marc Jones LONDON, June 13 (Reuters) - World stocks were pummelled and the dollar slumped on Thursday as a sell-off on global financial markets in thrall to central bank stimulus accelerated. European shares fell sharply at the open, dropping 1.3 percent after the second biggest fall in Jap