South Korean police Tuesday raided Google's local office to investigate whether the global search company used its mobile phone advertising platform to illegally collect private location data.

Investigators were sent to Google's Seoul office to secure evidence related to its "AdMob" platform, the head of the police cyber crime unit, Chang Byung-Duk, told AFP.

The raid followed allegations that Google's mobile advertising agency, AdMob, had illegally collected data on individuals' locations via smartphone applications, he said.

Investigators also raided the head office of local portal site Daum on suspicions that its advertising platform was used to collect location data, he said.

"During today's raid, we failed to secure evidence because a related server is located in the United States. Instead, Google officials promised to cooperate and provide information later," Chang said.

The raid came a week after South Korea's telecoms regulator launched an inquiry into Apple to see whether the US giant's collection of location data from its iPhone and iPad users violates privacy rules.

Apple dismissed claims it was tracking iPhone users. But it said it would fix software "bugs" that resulted in location data being unencrypted and stored for up to a year.

US lawmakers invited Apple and Google to attend a hearing on privacy this month following claims that the iPhone and Google's Android system were regularly tracking a user's location and storing the data.

Since it launched a Korean-language search site in 2000, Google has been striving to boost its presence against competition from local firms in one of the world's most wired societies.

But it has been hit by a previous probe in South Korea over data.

In January police accused Google of collecting personal data while producing its Street View mapping service, which allows users to see panoramic street scenes on the Google Maps site.

Google admitted its Street View cars, which have been cruising and taking photographs of cities in over 30 countries, inadvertently gathered fragments of personal data from unsecured WiFi systems.

But it said it did nothing illegal in South Korea and state prosecutors have yet to press charges.

Last month South Korean Internet firms filed complaints with the antitrust watchdog over Google's alleged practice of stifling competition in the local mobile phone search market.