A German court Tuesday jailed a married couple for spying for the Russian secret services for more than 20 years in one of the country's biggest espionage cases since the Cold War.

The pair, identified only by the code names Andreas and Heidrun Anschlag, were planted in the former West Germany from 1988 by the Soviet Union's KGB and later worked for its successor the SVR, the court heard.

U.S. Secretary of State John Kerry said Tuesday that the United States and Russia were committed to holding a peace conference on Syria but that it would likely take place after August.

Kerry, speaking after talks with Russian Foreign Minister Sergei Lavrov at a security meeting in Brunei, said "we both agree that the conference should happen sooner rather than later" to find a peaceful solution to the Syrian war.

A high-ranking North Korean official with long experience in nuclear talks left Tuesday for Russia, state media said, as the communist state steps up a diplomatic offensive after months of tension.

First vice foreign minister Kim Kye-Gwan was leading a delegation en route to the Russian capital, the official Korean Central News Agency said in a brief report.

Nineteen people, including children, died on Tuesday when a MI-8 helicopter crashed in the nearly impassable taiga in eastern Siberia, the latest disaster to hit Russia's accident-prone aviation industry.

A Moscow-based aviation committee, citing the surviving crew, said 19 of the 28 people on board were killed, but the emergencies ministry refused to confirm the toll.

An unmanned Russian Proton-M carrier rocket exploded Tuesday on takeoff at the Baikonur cosmodrome in Kazakhstan, in images broadcast live on national television.

Spectacular footage showed the rocket veering off its trajectory just seconds after its 6.38 am (0238 GMT) launch, before erupting into a ball of flames and releasing highly toxic rocket fuel into the air.

Fugitive U.S. intelligence leaker Edward Snowden on Monday accused U.S. President Barack Obama of "pressuring the leaders" of countries from which he has sought protection.

In his first public announcement since fleeing Hong Kong eight days ago, he accused Obama of ordering his Vice President Joe Biden to put pressure on leaders of countries where he was seeking asylum.

Russian President Vladimir Putin and U.S. President Barack Obama have ordered the chiefs of their respective security agencies to find a way out of the impasse caused by fugitive leaker Edward Snowden's stay in a Moscow airport, a senior official said on Monday.

"Of course (Putin and Obama) don't have a solution now that would work for both sides, so they have ordered the FSB director (Alexander) Bortnikov and FBI director Robert Mueller to keep in constant contact and find solutions," the head of Russia's Security Council, Nikolai Patrushev, said in an interview with state television channel Rossiya 24.

A top Russian lawmaker on Sunday declared it was "morally impermissible" to hand over to the United States fugitive intelligence leaker Edward Snowdon, who remains in a political limbo at a Moscow airport.

Snowden, the 30-year-old former contractor for the National Security Agency (NSA), has been living in the transit zone of Sheremetyevo airport for over a week, unable to fly on with a revoked U.S. passport or exit the airport without a Russian visa.

Russia accused Saudi Arabia and some other Gulf states on Thursday of funding "international terrorists and extremists" in the Syria conflict.

Moscow's angry statement came in response to accusations by Prince Saud al-Faisal, the Saudi foreign minister, that Russia was responsible for mass killings in Syria because of its military support for the regime.

Fugitive U.S. intelligence leaker Edward Snowden cannot leave the transit zone at a Moscow airport to fly on for another destination as his travel documents are invalid, a report said Thursday.

"Snowden does not have valid documents. He is not flying to Cuba or anywhere else for that matter," a source familiar with the situation told the state RIA Novosti news agency.