US manufacturing grew for the first time in four months, buoyed by a jump in new orders, according to a leading index.

The Institute for Supply Management, a trade group of purchasing managers, said that its index of factory activity rose to 51.5 in September. That's up from 49.6 in August.

A reading above 50 signals growth and below indicates contraction. The index had been below that threshold from June through August.

Stocks increased their gains after the report was released on Monday. The Dow Jones industrial average had been up roughly 100 points before the report came out. It jumped to 150 points up within 10 minutes of the release.

A measure of employment also increased, suggesting manufacturers added workers last month.

The increase could signal that manufacturing is picking up after a weakening this spring because of declining consumer demand and a drop in exports.

The improvement in the United States comes even as growth is slowing overseas. Europe's financial crisis has pushed many countries in the region into recession. Growth in emerging nations such as China and India has slowed.

China's manufacturing sector shrank in September, according to a survey by a Chinese trade group.

The US economy grew at an annual rate of just 1.3 per cent in the April-June quarter, down from a two per cent growth rate in the January-March quarter.

Most economists expect growth will stay near or below two per cent for the rest of this year. Growth at that pace is typically too weak to lower the unemployment rate.

The government will release the September employment report on Friday.

AP