SEOUL, Dec. 8 (Xinhua) -- South Korea has tightened up restrictions on the purchase of stakes in local telecom companies in a bid to help them stave off foreign hostile takeover bids, local Yonhap News Agency reported on Friday.

The National Assembly on Thursday passed an amendment to the electric communications law, which will likely go into effect in the second half of next year at the latest, Yonhap quoted an unnamed official as saying.

Under a revised law, anyone who wants to buy more than a 15 percent stake or become a controlling shareholder in local basic telecommunications service providers, which refer to firms that offer communications services such as fixed-line, mobile telephony and the Internet by using their own infrastructure networks, will be required to get approval from the information minister.

Currently, foreigners are not allowed to buy more than 49 percent in local communications service providers.

However, the United States is demanding South Korea to lift or ease the restriction on purchase on local communications firms.