By Andreas Rinke and Alexander Marrow
BERLIN/MOSCOW (Reuters) - Berlin prosecutors said on Friday they would investigate the case of Russian opposition politician Alexei Navalny, who is being treated in Berlin for suspected poisoning, and hand information to Moscow - if he agreed.
The German government had earlier said it would not investigate the case because the poisoning took place in Russia.
It has accused Russia of trying to poison Navalny and demanded an explanation from Moscow for what it said was the banned Soviet-era nerve agent Novichok found in his body by German doctors after he was airlifted from Russia for treatment.
Moscow has insisted it has seen no evidence he was poisoned and earlier on Friday said it would ask to send investigators to Berlin in response to the German demands.
The prosecutor's office in the German capital said it had been commissioned by the regional justice department "to provide legal assistance over the Russian request for legal assistance and to obtain information on the state of health of A. Navalny - subject to his consent".
Navalny, President Vladimir Putin's highest-profile critic, was flown to Germany last month after falling violently ill while travelling in Siberia. He is very unlikely to agree to Germany sharing information with the Russian government, which his supporters have accused of attempted murder.
Some senior German politicians have said Berlin should revoke support for Nord Stream 2, a big gas pipeline from Russia to Germany set to open next year. Such a move would amount to the most drastic economic penalty the West has imposed on Russia since the Soviet era.
The transport department of Russia's interior ministry in Siberia said it wanted to send investigators to work alongside German colleagues on the case, after reports that Navalny had emerged from a coma.
"This request will include an application for the possible presence of Russian internal affairs investigators ... and a Russian specialist when German colleagues are conducting investigations with Navalny, doctors and experts," the ministry said in a statement.
Russia has not opened a criminal investigation and is sticking to its position that it would first need hard evidence from Germany that Navalny was poisoned. Foreign Minister Sergei Lavrov said on Friday that German accusations over the case were "groundless".
Kremlin spokesman Dmitry Peskov said Moscow resented foreign pressure over the case. It had investigated the incident but did not have evidence that would lead to a criminal case, he said.
"Of course, we do not like it when other countries dictate to us what legal procedures we have at what point and on what basis to start them," Peskov said. "We cannot call these checks and inquiries a criminal case on the basis of analysis by a German laboratory ... legally, it is not possible."
The Russian interior ministry said transport police in Tomsk had established a timeline of events leading up to Navalny's illness. The ministry listed a hotel, restaurant, flat and coffee shop Navalny had visited, and said he had drunk wine and an alcoholic cocktail. In the days after he fell ill, Navalny's spokeswoman denied allegations he had consumed alcohol.
The Russian ministry said police had interviewed five of six people it said accompanied Navalny when he fell ill.
Police were looking for a sixth person the ministry named as Marina Pevchikh, a UK resident who flew to Germany on Aug. 22, and whose whereabouts it said were being established. This appeared to be a reference to Maria Pevchikh, an activist and ally of Navalny. Reuters was not immediately able to reach her for comment.
(Additional reporting by Anton Kolodyazhnyy and Vladimir Soldatkin; writing by Alexander Marrow, Peter Graff and Philippa Fletcher; Editing by Mark Trevelyan and Daniel Wallis)