South Korea has “detected signs” of North Korea “restoring an ancillary building” of its Dongchang-ri long-range missile launch site, which was partially disassembled last year, local media reported.

Quoting a government source in Seoul, South Korean news agency Yonhap reported on Wednesday Pyongyang had started dismantling the missile site, a launch pad and a railway linking them last June and “suspended it the following month, and that the signs of the North reassembling the building have recently emerged”.

The development came just days after Hanoi summit between U.S. President Donald Trump and North Korean leader Kim Jong-un which failed to reach any consensus on Korean peninsula denuclearization.

A Washington based think-tank, Beyond Parallel -- which works on Korean Unification -- also claimed that its commercial satellite imagery “acquired on March 2, 2019” shows that North Korea is “pursuing a rapid rebuilding” of the long-range rocket site at Sohae, according to Yonhap.

“This facility had been dormant since August 2018, indicating the current activity is deliberate and purposeful,” Yonhap quoted Beyond Parallel as saying in a report.

In his third meeting with South Korean President Moon Jae-in in Pyongyang last September, Kim had offered to “permanently dismantle the engine testing site and a launch pad at Dongchang-ri in the presence of international experts”, according to the news agency.

However, Yonhap said, Seoul's National Intelligence Service told the National Assembly's intelligence committee on Tuesday that the North “appeared to be putting back a roof and a door on a Dongchang-ri facility -- a sign of their restoration work”.

After the Hanoi summit, Trump had said that he could not meet Kim’s demand of complete lifting of sanctions which was contradicted by Pyongyang saying Kim only demanded partial abolition of sanctions to move forward.