SEOUL, South Korea —  South Korea is researching and developing cruise-missile technology, the defense minister told reporters Friday.

The statement by Defense Minister Yoon Kwang-ung follows North Korea's test of seven missiles on Wednesday.

Yoon did not elaborate on the reasons behind the effort, but it comes amid a general strengthening of the South's missile capabilities.

"We are making efforts in the research and development of a cruise missile," he said, according to a transcript released by the ministry.

In a South Korea-U.S. missile guideline signed in 2001, South Korea can only develop missiles with a range of less than 200 miles and a payload under 1,100 pounds.

But there is an exception in case of cruise missiles. South Korea can develop a cruise missile with no restriction on range as long as a payload is under 1,100 pounds.

Seoul has tested cruise missiles about a dozen times in the last three years, a military official said on condition of anonymity, citing government protocol.

The seven missiles Pyongyang fired Wednesday apparently fell harmlessly into the Sea of Japan, and U.S. officials said the long-range one — a Taepodong-2 believed capable of reaching U.S. soil — failed shortly after takeoff.