Wall Street jittery after anti-austerity Greek election victory

U.S. stock index futures turned to trade mostly higher early Monday, but uncertainty about the future of the euro zone hung over the market.

Global stock markets are now braced for further volatility after the radical left-wing party in Greece took around 36 percent of the vote and are now entering into talks with other parties to form a coalition.

Read MoreNew Greek government to keep markets on edge

A trader works on the floor of the New York Stock Exchange.
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A trader works on the floor of the New York Stock Exchange.

The results immediately hit the euro with the single currency falling to a fresh 11-year low of $1.1098, before recovering some ground, having already weakened dramatically last week after the European Central Bank announced new stimulus measures.European stock fluctuated between positive and negative territory for much of the morning session.

In Germany, Bundesbank President Jens Weidmann said he hoped "the new Greek government will not make promises it cannot keep and the country cannot afford", according to Reuters.

Major earnings on Monday include Citizens Financial, homebuilder DR Horton, Norfolk Southern and Seagate Technology before market open.

Investors will also be watching for Microsoft and Texas Instruments fourth quarter earnings after the bell.

Ashland, Plum Creek Timber, BBCN Bancorp, Brown & Brown, Graco, MicroStrategy and Packaging Corporation of America are amongst the firms also reporting.

There are no major data releases on Monday. This week, investors will be eyeing Wednesday's conclusion of the latest Federal Reserve policy meeting, where policy and forecasts are likely to remain unchanged, but given the further drop in the oil price since the Committee met in mid-December, the post-meeting statement should be closely watched.