South Korean tech giant Samsung said Tuesday its smartphones and tablets have received a US government security clearance allowing officials to use them to send classified information.

The Samsung devices were placed on a list of gadgets approved by the National Security Agency for managing classified information. The Boeing Black phone is also on the list.

The newly approved devices include the Galaxy S4, Galaxy S5, Galaxy Note 3 and Galaxy Note 10.1 tablet. They can all use Samsung's Knox software, which adds a layer of security for data on the devices.

Samsung products had already been on the US Defense Department list of approved hardware for "sensitive but unclassified" use, but the latest approval expands that to more secret information.

The approval "proves the unmatched security of Samsung Galaxy devices supported by the Knox platform," said JK Shin, who heads the company's IT and mobile business.

With the latest approval, Samsung -- the world's largest smartphone maker -- can now seek a wider range of US government contracts for its mobile devices.