Seoul, Oct 30 (IANS): North Korea has dug a new tunnel at its nuclear test site in the northeastern part of the country, a source from the South Korean government said on Friday.

"An increased movement of people and cars has been spotted at the nuclear site. North Korea appears to be in the process of digging another tunnel," the official said, without giving further details.

This development could indicate that Pyongyang is preparing for its fourth nuclear test, after the previous three tests (in 2006, 2009 and 2013) were conducted at the same base at Punggye-ri, in North Hamyong province, which led to severe sanctions from the UN Security Council, EFE news quoted the official as saying.

However, South Korea is yet to officially confirm the development.

The Kim Jong-un regime of North Korea has reiterated on numerous occasions that it will continue with their advances in developing nuclear arms.

The news about the possible digging of the tunnel comes before the heads of South Korea, China and Japan are to meet Sunday in Seoul for their first trilateral summit in three years, during which North Korean nuclear policy is expected be the agenda's main focus.