AIX-EN-PROVENCE, France, July 6 (Reuters) - Global economic activity should accelerate in 2015 after being gloomy at the start of 2014, IMF chief Christine Lagarde said on Sunday, adding that the Fund saw no brutal slowdown in China.

Lagarde said the impact of central banks' accomodative policies on demand had its limits and countries should also act to help growth - in particular with investment on infrastructure, education and health - as long as their debt would still be sustainable.

The IMF's update of its global economic outlook, expected later this month, will be slightly different from the forecasts published in April, she said.

Lagarde estimated that growth in China this year would be between 7 and 7.5 percent.

(Reporting by Ingrid Melander and Alexandre Boksenbaum-Granier, editing by William Hardy)