By Barbara Kollmeyer, MarketWatch

MADRID (MarketWatch) -- U.S. stock futures posted moderate gains on Tuesday a day after Wall Street suffered heavy losses, with J.P. Morgan Chase & Co. off after results and Citigroup Inc. still to come.

Futures for the S&P 500 index (SPZ4) rose 5 points to 1,870.60, while those for the Dow industrials (DJZ4) climbed 41 points to 16,273. Futures for the Nasdaq 100 index (NDZ4) gained 13.75 points to 3,812.50. Stock futures had earlier slipped into negative after downbeat German sentiment data.

Extending last week's losses, volatile trading on Monday ended with the S&P 500 (SPX) dropping 1.6% to 1,874.74. Like other major benchmarks, the S&P 500 is now trading below its 200-day moving average of 1,900. Vote here: Does this stock slump have further to go?

James Hughes, chief market analyst for Alpari U.K., said he's wary because he sees traders targeting old stories, such as concerns over slow global growth and its effect on earnings. "When traders look for excuses for why the market is falling, [it] is always a worrying time and would point to me as an indication that we could see much more negativity to come," he said in a note.

Earnings in focus: The tide could change with Tuesday's earnings batch, the first busy day in the third-quarter reporting season. Ahead of the bell, J.P. Morgan Chase & Co. (JPM) swung to a third-quarter profit as the bank rebounded from a year-earlier period that saw it weighed by big legal charges. The bank's profit per share was $1.36 and revenue rose to $24.2 billion, against expectations for per-share earnings of $1.38 on revenue of $24 billion, according to analysts surveyed by FactSet.

The earnings were scheduled to be released around 7 a.m. Eastern Time, but showed up on the Internet several hours earlier on a third-party website. J.P. Morgan shares eased 0.4% in early premarket trading.

Still to come, Citigroup (C) is expected to report per-share earnings of $1.12 on revenue of $19.16 billion.

Wells Fargo & Co.(WFC), Domino's Pizza Inc. (DPZ) and Johnson & Johnson (JNJ) are among the other names reporting.

Among other stocks in focus, Versar Inc. (VSR) was surging almost 60% in premarket trading. Its PPS unit makes hazmat suits and mobile decontamination shelters. Other stocks linked to concerns over the Ebola virus continued a pattern of pushing higher. Lakeland Industries Inc. (LAKE) and Alpha Pro Tech Ltd. (APT) were trending higher. Ebola stock trading volumes should raise red flags

Other markets:European stocks fell after a key sentiment survey out of Germany turned negative. Burberry Group PLC shares dropped after the luxury-goods maker posted a rise in sales, but cited unfavorable foreign exchange headwinds and Chinese weakness. U.K. inflation fell to a five-year low. The European Court of Justice has begun holding a hearing on the European Central Bank's Outright Monetary Transactions bond-buying program.

In Asia, the Nikkei 225 index sank 2.4%, falling below the 15,000 level and skidding to two-month lows.

Crude-oil prices(CLX4) drifted lower, and gold(GCZ4) inched up, while the dollar ((USDJPY) pulled back from an overnight slip against the Japanese yen.

Subscribe to WSJ: http://online.wsj.com?mod=djnwires