London shares tumbled more than 100 points in early trading after more downbeat Chinese economic data.
The FTSE 100 Index fell 105.98 points to 6141 following another contraction in manufacturing figures overnight.
Markets were expecting a fall, but analysts said the data simply provided more confirmation that Chinese economic momentum was slowing down.
Chief market analyst at foreign exchange group FXTM, Jameel Ahmad, said: "Chances of GDP growth falling below the government’s target are actually intensifying each time an economic announcement is released from China, mainly because all data is consistently pointing towards economic momentum declining in this major economy."
There was mixed economic news from Europe, where stronger Purchasing Manager's Index (PMI) numbers from Germany and Spain contrasted with weaker figures in the UK, France and Italy.
In Germany, manufacturing PMI figures hit a 16-month high in August. But in the UK, the headline seasonally adjusted Markit/CIPS PMI dipped slightly to 51.5 in August, from 51.9 in July and well below the average of about 54 since the start of 2013.
Senior UK economist Samuel Tombs said: "August’s UK CIPS report on manufacturing shows that the strong pound is crimping exporters and so suggests that the major support net trade provided to GDP growth in the second quarter will be a blip."
In thin corporate news, RSA Insurance (LON:RSA) was outperforming the market after talk that the UK firm, which has received a takeover approach from Swiss rival Zurich Insurance, could face a rival bid from Allianz of Germany or Generali of Italy.
RSA shares fell 2p to 512p but Aviva (LON:AV.) was off 12.8p at 471p, Prudential (LON:PRU) reversed 41p to 1377p and Admiral (LON:ADM) retreated 16p to 1534p.
Shares in Northcote Energy (LON:NCT) rose by a fifth to 0.18p after the US oil explorer reported better-than-expected drilling results at a well in Louisiana.
Satellite operator Inmarsat (LON:ISAT) was 1.5p higher at 982.5p as it confirmed the successful launch into orbit of its third Global Xpress satellite.