Two Chinese tech firms have clashed over a new wireless router with a special setting for pregnant women.

Qihoo 360 unveiled the device, an upgrade to an existing product, which has three settings it describes on its website as wall penetration, balance and "pregnant women".

The third setting reduces radiation emitted by the router by 70%, the firm claims.

However, tech giant Xiaomi has accused Qihoo of scaremongering.

"The so-called pregnancy mode is just a marketing tactic. Wi-fi usage is safe, so please rest assured when using it," Xiaomi said in a post on social media site Weibo.

The two firms are fierce rivals, and Xiaomi has also recently launched a new router product, which offers six terabytes of storage and high-speed connections but does not include this setting.

Zhou Hongyi, Qihoo's chief executive, said at Qihoo's P1 launch event that the firm was "targeting people who are afraid of radiation", reported the South China Morning Post.

There is controversy surrounding the health effects of electromagnetic signals such as wi-fi on humans - although the low-level non-ionising kind used by telecommunications devices is scientifically said not to cause significant harm.

The BabySafe Wireless Project is a US-based campaign group which argues that wireless radiation does pose a risk to pregnant women and their unborn babies.

However, the World Health Organization says that the evidence so far does not support the claims.

"The overall weight of evidence shows that exposure to fields at typical environmental levels does not increase the risk of any adverse outcome such as spontaneous abortions, malformations, low birth weight, and congenital diseases," according to the WHO  website.

"Based on a recent in-depth review of the scientific literature, the WHO concluded that current evidence does not confirm the existence of any health consequences from exposure to low-level electromagnetic fields."