South Korea's Yonhap news agency has reported that North Korea has erected a new, taller launch tower at its missile base, claiming it will be used for firing a long-range rocket to mark an important national anniversary in October.
South Korean officials said the upgraded launch pad could fire a missile larger than Unha-3, referring to the long-range rocket fired in 2012 from the base.
"Our military is closely monitoring and tracking North Korea's movement related to a possible missile launch including extension work on a launch tower at its missile base in Tongchang-ri, North Korea," said South Korea's defence ministry spokesman Kim Min-seok at a ministry news briefing on Wednesday.
The 67-metre tower is located near the country's west coast and was previously used for successful launch of a long-range rocket and putting an object into orbit three years ago.
Yonhap reported that a possible launch of a long-range rocket could coincide with the 70th anniversary of the founding of the North's ruling Workers' Party on October 10.
The report came as North Korea rejected calls from China and South Korea to initiate dialogue with the United States for denuclearisation, similar to the one with Iran on Tuesday, stating that its nuclear programme was an "essential deterrence" against a hostile US foreign policy.
"It is not logical to compare our situation with the Iranian nuclear agreement because we are always subjected to provocative US military hostilities, including massive joint military exercises and a grave nuclear threat," North Korea's Foreign Ministry said in a statement.
North Korea is banned by the United Nations Security Council from conducting tests that use ballistic missile technology and also under heavy sanctions due to its ongoing nuclear and ballistic missile programmes.
Talks between North Korea, South Korea, the United States, Russia and Japan over the issue have been at a standstill since 2009 as the reclusive country has defied scepticism and international warnings not to pursue such a programme.