"The plan to build an underwater pipeline came up during talks with Gazprom President Alexei Miller and experts at Russia's Pacific Ocean Institute in Vladivostok last week," Choo Kang-soo, head of Korea Gas Corp., said Wednesday to the Yonhap news agency.

In September, Korea Gas announced it will import 7.5 million tons of gas annually from Russia starting in 2015 using an overland pipeline through North Korea.

However, Yonhap quoted Choo as saying Russian gas company executives hinted Pyongyang officials they met with recently may not support it because of strained relations between the two Koreas under South Korean President Lee Myung-bak's conservative government.

Earlier this week, North Korea said it will tighten crossings through the border with the South beginning next month, the report said.

Choo said the Russians suggested an undersea pipeline linking Vladivostok with either Samcheok on South Korea's east coast or Busan, the country's largest port. He said while an undersea pipeline would cost more "it is not technically impossible," the report said.

Choo indicated the overland route may still be possible as North Korea also needs access to natural gas.