Seoul has chosen Boeing's AH-64E Apache Guardian helicopters for $1.6 billion amid tensions with North Korea, the South Korean Defense Acquisition Program Administration said.

The fleet of 36 new advanced attack helicopters will play a crucial role in countering North Korean amphibious infiltrations into western border islands should they occur, a report by The Korea Herald newspaper said.

Boeing's four-blade twin-engine Apache beat Bell's AH-1Z and the Turkish Aerospace Industries T-129, a joint development with AgustaWestland as the primary partner and based on its A129 Mangusta.

"We can beef up our military strength that might be weakening due to (our) aging helicopters," the DAPA said in a statement.

"This new helicopter fleet will help handle the threat posed by North Korea's mechanized forces and possible provocations such as maritime infiltrations."

Sustainment cost for the army's Apaches -- to be deployed from 2016-18 -- is expected to be higher than for the 500MD, made by Hughes Helicopters and McDonnell Douglas Helicopter Systems, and Bell's Cobra AH-1S attack helicopters South Korea operates, the DAPA added.

Last month British engine manufacturer Rolls-Royce said it is selling its interest in the RTM322 engine program for powering Apache, Merlin and NH helicopters for around $382.5 million in cash.

The sale of its 50 percent interest will be to Turbomeca of France, a member of the Safran group, Rolls-Royce said.

Turbomeca is progressively buying Rolls-Royce shares and will eventually hold sole interest in the program by the time the sale is expected to be complete at the end of this year.

Rolls-Royce said Turbomeca will assume full responsibility for the design, production and support of the RTM322 engine, which powers the Apache, the EH101 Merlin from AgustaWestland and the NH90 helicopters made by NHIndustries.

"Rolls-Royce will provide full assistance to Turbomeca during the multiyear transition period to ensure all RTM322 customers continue to receive effective support."

The RRTM Adour engine program which powers the Hawk and Jaguar aircraft is unaffected by the agreement with Turbomeca.

The Herald report said the Apache's speed of upward of 160 mph will counter communist North Korea's use of attack hovercraft.

The north has positioned around 130 hovercraft close to the demilitarized zone in Hwanghae province, next to the Yellow Sea.

The Herald report said the hovercraft can travel up to 60 mph through mudflats among the islands along the DMZ.

But how many hovercraft the North is operating is open to question.

In March, U.S. journalists suspected a picture released by North Korea's government-run Korean Central News Agency was digitally altered to add more hovercraft, a report by The Atlantic said.