Akhir 11, 1432 H/March 16, 2011, SPA -- European share markets ended a volatile trading day Wednesday amid deepening concerns about the threat posed to global economic growth by the nuclear crisis in Japan, according to dpa. After seesawing through the day, the benchmark Stoxx Europe 600 index closed down 1.55 per cent at 262.18 points after initially nudging up in the morning following a rebound in stocks in Tokyo. The Stoxx 600 index is now 6.75 per cent down on the week in the wake of the economic shock caused by last Friday's magnitude-9.0 earthquake that rocked north-eastern Japan, triggering a massive tsunami and plunging the world's third biggest economy into a nuclear crisis. Also hitting European shares were signs of fresh financial turmoil in Portugal after Moody's downgraded the nation's bond ratings late on Tuesday. This helped to trigger a fall in bank shares across Europe. The downgrade also helped to undercut demand for both a debt auction launched by Lisbon and the euro. The common currency was down 0.4 per cent as the trading day came to an end. While shares in London finished the day down 1.7 per cent, the Frankfurt and Paris bourses both closed more than 2 per cent off. Adding to the brittle mood, shares in New York fell 1.5 per cent 11,682 as the trading day continued on the world's biggest stock market. The oil price also renewed its rise Wednesday in the wake of the outbreak of new tensions in the Arab world. New York crude oil nudged up 1.2 per cent to 98.26 dollars a barrel in late European trading. The volatile trading day in European shares came after Japan's Nikkei 225 Stock Average clawed back some of the big losses it ran up on Tuesday by surging by 5.6 per cent. Japan's central bank stepped up its efforts to stabilize the country's financial system Wednesday by pumping an additional 5 trillion yen (61.5 billion dollars) into money markets. Shares across Asia posted more modest gains with stocks in Shanghai gaining 0.46 per cent and 0.7 per cent in Sydney as bargain hunters also began moving back into stock markets.