An important gauge of China’s manufacturing sector has weakened sharply, adding to the pressure on the government to take more decisive action to support the flagging economy.

The official purchasing managers’ index for manufacturing fell to 50.4 in May, its lowest in five months, from 53.3 in April. Although it was the Chinese PMI’s sixth straight month above the 50 level, which signals an expansion of activity, the fall in the index highlighted a clear softening of growth momentum.

As the first item of official economic data for May, the PMI offers a timely glimpse into how the Chinese economy performed over the past month. Many analysts and officials had believed that China was on track for a “soft landing” until a raft of poor data in April led to a flurry of growth forecast downgrades.