Economists have raised their forecasts for Singapore's full-year economic growth, after the economy grew more than expected in the July to September quarter.

The economy expanded by a better-than-expected 5.8 per cent in the third quarter. the Trade and Industry Ministry said on Thursday. The ministry also revised its growth forecast for the full year upwards, to between 3.5 and 4 per cent.

ANZ economist Daniel Wilson said the latest data "reinforces the narrative that external demand is broadening and strengthening". He expects the economy to grow 4 per cent for the full year, up from a previous estimate of 3.5 per cent.

Citi economist Kit Wei Zheng is also tipping 4 per cent growth this year, an upgrade from his earlier forecast of 3.6 per cent.

Bank of America Merrill Lynch economist Chua Hak Bin said the manufacturing sector is " finally staging a more visible improvement after a long lull".

Third quarter economic growth was boosted by a strong recovery in manufacturing, which expanded 5.5 per cent over the same period last year, up from just 1.3 per cent growth in the second quarter.