The US Department of Justice has approved Google's acquisition of mobile phone and tablet maker Motorola Mobility for about $12.5 billion (£7.9 billion), following the European Commission's approval earlier this week.

Google is still waiting for approvals from China, Israel and Taiwan before the deal is final. Canada's investigation is also ongoing. The search giant still says it hopes the acquisition will close in "early 2012".

The DOJ also approved bids by Apple, Microsoft and Research in Motion to purchase some Nortel Networks patents, as well as Apple's purchase of some Novell patents.

The DOJ's Antitrust Division has "determined that each acquisition is unlikely to substantially lessen competition," the agency said. The DOJ has closed its investigations into the three deals.

Google's acquisition of Motorola is unlikely to cause major changes to the mobile industry, the DOJ said.

"The evidence shows that Motorola Mobility has had a long and aggressive history of seeking to capitalise on its intellectual property and has been engaged in extended disputes with Apple, Microsoft and others," the DOJ said. "As Google's acquisition of Motorola Mobility is unlikely to materially alter that policy, the division concluded that transferring ownership of the patents would not substantially alter current market dynamics."

Apple's acquisition of Novell patents that are important to the open source community is unlikely to change the market because Novell had committed to providing the patents with royalty-free licences for use in Linux, the DOJ said.

The acquisition of mobile patents by Microsoft and RIM should not hurt competition because the two companies "low market shares in mobile platforms would likely make a strategy to harm rivals... unprofitable," the DOJ said.