A former FSB officer, Alexander Litvinenko died November 23 in a London hospital from a lethal dose of the radioactive substance polonium-210.
Dmitry Kovtun, a former colleague turned businessman, met with Litvinenko in the British capital shortly before he fell ill and was himself later diagnosed with radioactive poisoning.
The spokesman said the office has not yet received an official request for legal assistance from Germany, although it was reported Tuesday that Germany had made one.
"In case [such a] request arrives, the Prosecutor General's office will consider it in line with the norms of international and Russian laws. If need be, we will assist our German colleagues," he said.
Police in Hamburg launched an investigation of Kovtun after traces of radiation were detected at several sites he visited between October 28 and November 1, including at his ex-wife's apartment. German investigators suspect Kovtun, who has a German residence permit, of illegally transporting nuclear materials.
In Russia, Kovtun is being treated as a witness in the case of Litvinenko, a Federal Security Service defector and outspoken Kremlin critic with ties to exiled Russian oligarch Boris Berezovsky.
Another key witness in the case, Andrei Lugovoi, also a former security agent and Kovtun's business partner, was questioned Monday by Scotland Yard detectives and Russian investigators.
Both men met with Litvinenko in London around the time he fell ill.
