The South Korean government on Tuesday said that it does not know if North Korea's Kim Jong-un was visiting Beijing.

A South Korean presidential office spokesperson said that the government was closely monitoring the situation, studying all possibilities and communicating closely with the countries involved, reports Efe news.

On Monday, a Japanese TV channel showed images of an armoured train similar to the ones used by the North Korean leaders to reach Beijing's main station.

In Beijing, where the government has not yet made any comments, a heavy security presence has been observed around the Diaoyutai State Guesthouse, where Kim might be staying.

Access to the Tiananmen Square has been restricted, which is common protocol when there is a state meeting with a foreign president in the Great Hall of the People.

The North Korean media also did not report on the supposed visit.

The development comes ahead of the proposed summit between Kim Jong-un and South Korean President Moon Jae-in in April, and a possible meeting between the North Korean leader and US President Donald Trump in May.

The meeting in April would be the first inter-Korean summit in 11 years while the one in May would be the first ever summit between a North Korean leader and a sitting US president.