( CNN) US President Donald Trump's Russia problems seem to be getting worse by the week — Attorney General Jeff Sessions has become the most recent senior Trump official to be found within a murky web of ties and contacts to Russia.

While some of Trump's Russia issues are mere nuisances, others could lead to more serious political — and perhaps even legal — consequences for the administration, experts say.

KEY PLAYERS

Here's what CNN has reported on the contacts and the linkages between former and current Trump aides and key figures in Russia and Ukraine.

CAMPAIGN CONTACTS WITH RUSSIA

Sessions told Congress during his confirmation hearing that he “did not have communications with the Russians, “ but now admits that he had two sessions with Russian Ambassador Sergey Kislyak. He insists the meetings were not to discuss the campaign.

What to know about Sergey Kislyak

More casualties as Putin allies bombard eastern Ukraine

Is Russia's honeymoon with Trump over?

What was Russia's involvement in US election?