The Dow Jones posted strong gains in early trading on Thursday as a cooling operation at the tsunami-hit Fukushima Daiichi nuclear plant eased investor fears.
The Japanese yen hit a record postwar high against the US dollar this morning, reaching 79.32, although commentators expect the rally to be temporary.
A major earthquake in Japan has rocked markets, which were already fragile yesterday as the FTSE 100 hit a five-week low.
Markets fell across the board at the start of trading today, after Moody's downgraded Spain's government debt from Aa1 to Aa2 with a negative outlook.
The FTSE100 fell in early trading as concerns over EU debt problems offset any reassurance the market might take from easing oil prices.
Most European bourses look cautiously positive in morning trading ahead of the US non-farm payrolls data for February.
World markets have responded positively to Brent crude futures falling by more than $3 after the Arab League said it was considering stepping in to end the crisis in Libya.
Ongoing disruption in the Middle East and the higher oil price has dragged on global markets, with many seeing losses of more than 1%.
Billionaire investor Warren Buffett's bullish outlook for the US has boosted markets, pushing the Dow Jones up 96 points and the FTSE back above the 6,000 mark.
Libya unrest has driven Brent crude oil to a 29-month high of $119, causing Asian markets to fall overnight and European stocks to slump as investors take profits.