US benchmark West Texas Intermediate for August delivery rose 10 cents to $105.44 while Brent crude gained nine cents to $112.38 in afternoon trade.

With few leads in Asian trading, focus is on the US Energy Information Administration's weekly stockpiles report to be released later Wednesday, analysts said.

Reserves are expected to have fallen 1.7 million barrels in the week ended June 27, according to analysts polled by the Wall Street Journal.

Gasoline stockpiles likely rose by 200,000 barrels, and stocks of distillates, which include heating oil and diesel, are expected to have climbed 800,000 barrels.

Singapore's United Overseas Bank (UOB) said oil prices retained support "on upbeat manufacturing data in China".

Chinese manufacturing activity expanded at its fastest pace this year in June, an official survey showed Tuesday, in a sign that Beijing's attempts to tackle slowing growth in the world's number two economy and top energy consumer are gaining traction.

UOB said concerns are easing over a possible supply disruption in major crude producer Iraq.

Islamist militants have overrun swathes of territory in Iraq in a lightning offensive since June 9, but have so far yet to directly threaten the key oil-producing region in the country's south.