North Korea's foreign minister has arrived in Burma for talks with top leaders, reports from the region say.
It is thought to be the first visit by Pak Ui-chun since the two countries resumed formal ties in 2007.
Mr Pak will travel to the capital, Naypyitaw, for talks with counterpart Nyan Win, officials said.
Analysts have raised concerns in recent months that Burma is co-operating with North Korea to develop nuclear technology. Burma denies this.
Last week US Secretary of State Hillary Clinton said she was concerned about military ties between the two authoritarian states.
"We know that a ship from North Korea recently delivered military equipment to Burma and we continue to be concerned by the reports that Burma may be seeking assistance from North Korea with regard to a nuclear programme," she said at a regional summit in Hanoi.
Last month a report by Oslo-based Democratic Voice of Burma said that Burma was trying to develop a nuclear weapons programme.
It based its report on testimony, files and photographs provided by Major Sai Thein Win, a Burmese soldier and mechanical engineer who defected.
The Burmese government described the report as "baseless allegations".
North Korea has conducted two nuclear tests. Talks between it and the international community on ending its nuclear programme have been stalled for months.
The North Korean foreign minister is expected to spend four days in Burma, reports said.
Burma severed ties with North Korea in 1983, following an attack by North Korean commandos on the South Korean president as he paid a visit to Rangoon.
The president, Chun Doo-hwan, survived, but 21 other people were killed.