Apple has for the first time held talks with environmental campaigners who accuse the company's Chinese manufacturers of widespread pollution, participants said Wednesday.

The maker of the iPad and iPhone agreed to meet five Chinese environmental groups after they issued a report in August that alleged rampant pollution at dozens of factories believed to be producing products for Apple.

One of the campaigners, Ma Jun, praised the talks as a "step forward" but criticised Apple for refusing to identify its suppliers in China -- a policy pressure groups say enables the electronics giant to evade scrutiny.

"This was the first time that they sat down with all five of us to discuss the report, so this was a step forward," said Ma, director of the Institute of Public and Environmental Affairs.

"Despite this they consider that the pollution from these 15 companies is a commercial secret. So we don't know the names of the 15 companies and we can't verify the steps they are making to curb pollution."

In the report, the environmental groups alleged that companies they believed to be supplying Apple were discharging toxic substances that were harming workers and local residents.

Apple, whose iPhones and iPads are hugely popular among China's growing middle class, declined to comment on the meeting directly.

Apple has in the past confirmed that two Chinese factories, one owned by Taiwanese technology giant Foxconn and the other by WinTek, also a Taiwanese company, were making its products.

It acknowledged the FoxConn plant after a series of worker suicides there and has said that last year 137 workers at the WinTek plant suffered "adverse health effects" when exposed to a chemical substance called N-hexane, used to clean screens.

"We require that our suppliers provide safe working conditions, treat workers with dignity and respect, and use environmentally responsible manufacturing processes wherever Apple products are made," said company spokeswoman Carolyn Wu.