New York's main contract, light sweet crude for delivery in August, dipped 91 cents to $74.72 a barrel.
Brent North Sea crude for August sank $1.01 dollars to $74 per barrel in early afternoon London trade.
"Crude oil prices extended losses ... Amid expectations of a weaker oil demand from China, following the poor Chinese PMI figures this morning that hurt sentiment for risk appetite," said Sucden analyst Myrto Sokou.
Manufacturing activity in China slowed in June, official and independent surveys showed today, suggesting that government efforts to cool the fast-growing economy are working.
The HSBC China Manufacturing PMI, or purchasing managers index, fell to 50.4 last month from 52.7 in May, the bank said. A reading above 50 means the sector is expanding, while below 50 indicates an overall decline.
A separate survey released by a government agency today showed manufacturing activity slowed to 52.1 in June from 53.9 in May.
Oil had also fallen on Wednesday on weak jobs and inventory data in the United States, the world's biggest energy consumer, followed by number two China.
The market reacted to news that the US private sector created only 13,000 jobs in June compared with expectations of 61,000.