Wall Street closes mostly higher

US stocks have closed mostly higher as investors welcomed upbeat comments from Federal Reserve chair Janet Yellen on the state of the US economy.

However, tech stocks weighed on markets, with Twitter again leading the Nasdaq lower.

At the closing bell, the Dow Jones Industrial Average jumped 117.84 points, or 0.72%, to 16,518.86.

The broad-based S&P 500 advanced 6.72 points, or 0.56%, at 1,878.21, while the tech-heavy Nasdaq Composite Index slipped 13.09 points, or 0.32%, to 4,067.67.

Microblogging site Twitter saw its stock again a target of short sellers, sinking 4% to mark the third straight day of record lows. Earlier it had given up 8% on the back of losses of close to 18% yesterday.

Shares in the firm remain above their November listing price, however.

The tail-end of earnings season saw video game developer Electronic Arts beat expectations and surge over 15%, while grocery store Whole Foods Market plunged over 15% after cutting its outlook for the full-year.

Another drag on the market was news that labour productivity had fallen more than expected in the first quarter while wages had risen above expectations, although this was offset by comments from Fed chair Janet Yellen that hinted at a strongly growing economy.

Ms Yellen tipped "solid" growth, with GDP expansion expected to beat last year's growth despite a soft first quarter number.

Adding to positive sentiment was a rare sign that Russian President Vladimir Putin did not want to further escalate tensions in Ukraine as he called for dialogue between pro-Russian separatists and Kiev.