North Korea has test fired four short-range ballistic missiles from the Gitdaeryeong area, off its south-east coast, reportedly in response to the on-going South Korea-US annual military exercises.
An unnamed South Korean Government source was quoted by Yonhap News agency as saying that the missiles are believed to be part of the scud series.
"We first believed they were an improved version of the KN-02 ground-to-ship missile, but we now believe they are scud series missiles, as they have a range of more than 200km," the source said.
However, another military official said the exact missile type determination requires additional analysis, as the projectiles could also be advanced versions of the KN-02 or new 300mm calibre rockets fired from a multiple rocket launcher system.
If confirmed, the launch would be North Korea's first scud missile firing since July 2009, according to the news agency.
Three types of scud missiles are reportedly in service with North Korea, namely the Scud B with a range of 300km, the Scud C with a range of 500km and the Scud D with a range of 700km.
Calling the launch "intentional and a kind of provocation", the South Korean ministry of national defence (MND) has ordered the military to "maintain tight vigilance in preparation for additional launches or any military provocation from the North."
Pyongyang considers the annual key resolve and foal eagle drills a provocation and a prelude to an invasion, despite the US's insistence that they are aimed at enhancing the alliance's operational readiness.
The war games involve a large number of US and South Korean military personnel and are scheduled to conclude in April, The Guardian reports.