By Yi Whan-woo

Sin Hong-chol

North Korean Vice Foreign Minister Sin Hong-chol arrived in Moscow, Saturday, to meet Russian Deputy Foreign Minister Igor Morgulov this week, according to the Russian foreign ministry, Sunday.

Sin's trip comes after several Russian diplomats hinted at North Korean leader Kim Jong-un's visit to Moscow in line with Russian President Vladimir Putin's invitation.

And speculation is rampant that Sin, who handles Pyongyang-Moscow relations, may begin talks with Morgulov for the first summit between their leaders.

Kim and Putin have not yet met.

The Russian foreign ministry said Sin and Morgulov have met routinely to discuss bilateral issues. It did not give details on the agenda to be discussed this week.

Sin also kept mum when asked whether he will prepare for Kim's Russia visit, after arriving at Sheremetyevo International Airport in Moscow, Saturday.

"It's possible Sin and Morgulov will talk about Kim's travel to Russia in addition to other issues they have discussed routinely," a diplomatic source said.

In May, Russian Foreign Minister Sergey Lavrov visited Pyongyang and delivered Putin's invitation to Kim to visit Russia.

The North Korean leader, however, has not confirmed whether to accept the invitation.

Valentina Matviyenko, speaker of the Federation Council of the Russian Federal Assembly, said Kim may travel to Moscow within this year, after meeting him in Pyongyang in September.

Matviyenko was there as Putin's envoy for North Korea's celebration of the country's 70th founding anniversary.

Some diplomatic sources also said Kim may go to Russia by the end of this year.

They pointed out the United States is likely to delay its next summit between Kim and U.S. President Donald Trump to early next year from December.

Morgulov previously said Pyongyang and Moscow have been coordinating schedules for a possible Kim-Putin summit.