Global stock indexes fell today, continuing a brutal start to 2016, as China's market tumbled again and the decline in oil prices worsened.

The main US indexes gave up earlier gains in morning trading, which came after the S&P 500 and the Dow posted their worst five-day start to the year in history.

The pan-European FTSEurofirst 300 index was off 0.2%, also after rising earlier in the session.

Fears over China's economy contributed to last week's declines, and the main Shanghai stock indexes each ended down more than 5% today.

Perceived missteps by China's authorities have stoked concerns in global markets that Beijing might lose its grip on economic policy, even as the world’s second largest economy looks set to post its slowest growth in 25 years.

"The Chinese situation sets the agenda right now in combination with oil prices," said Hans Peterson, global head of asset allocation at SEB investment management.

The Dow Jones industrial average was down 30.75 points, or 0.1%, at 16,315.7, the S&P 500 shed 6.77 points, or 0.35%, to 1,915.26 and the Nasdaq Composite lost 25.97 points, or 0.5%, to 4,617.66.

Investors were looking to US corporate earnings to help provide confidence, with Alcoa posting results later on Monday and major banks reporting later this week, despite expectations for a second quarter of overall declining earnings.

"The mentality has been pretty negative and I don't see that changing this morning or today until there is more meat on the bones from a data standpoint," said Michael James, managing director of equity trading at Wedbush Securities in Los Angeles.

MSCI's broadest gauge of stocks globally slipped 0.6%, after registering its biggest weekly decline in more than four years.

Oil prices plummeted to 12-year lows, with US crude futures falling to the lowest since late 2003, as traders cited fears over slowing demand in China and a growing inventory glut.

US crude prices fell 4.3% to $31.72 a barrel, while benchmark Brent dropped 5% to $31.83 a barrel.

"China has torpedoed the hopes of the optimists," David Hufton, of oil brokers PVM Oil Associates, said in a note.

The US dollar was up 0.2% against a basket of currencies, while the euro fell 0.7% against the dollar.

"Modestly improved risk sentiment was enough to cause the euro to lose some ground against the US dollar," said Joe Manimbo, senior market analyst at Western Union Business Solutions in Washington.

Spot gold fell 0.5% but still hovered at more than two-month highs.