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BEIJING, April 1 (Reuters) - Activity in China's factory sector edged up slightly in March, a government survey showed, though the figure is unlikely to dispel concerns that the world's second-largest economy slowed more than expected in the first quarter.

The official Purchasing Managers' Index increased to 50.3 in March from February's 50.2, the National Bureau of Statistics said on Tuesday.

That was in line with economists' forecasts, and just above the 50-point threshold separating growth from contraction.

A string of weak economic indicators this year, including falling exports and a preliminary PMI survey last week by HSBC and Markit Economics that put factory activity at an eight-month low, have pointed to the Chinese economy losing some momentum.

This in turn has raised speculation that the government would step in to support growth. Premier Li Keqiang said last week the necessary policies were in place and the government would push ahead with infrastructure investment. .

"We're still in a subdued part of the cycle," said Louis Kuijs, chief China economist at the Royal Bank of Scotland.

"I still don't think the downward pressures are tremendous, but they are large enough for the government to really start to talk about the need to support growth."

The final version of the HSBC/Markit survey is due at 0145 GMT on Tuesday.

(Reporting By Adam Rose; Editing by Jonathan Standing and John Mair)