The attack came as U.S. officials were expected to hold peace talks with Ukrainian and Russian officials in the coming days.

The strikes occurred in a strategic maritime corridor, raising concerns about energy security and navigational safety.

Ukraine’s chief negotiator, in an exclusive interview, says conceding sovereign territory is off-limits in peace talks.

President Donald Trump says Ukraine and Russia are making progress in peace talks but called the conflict difficult to solve on Tuesday night.

"If this is true, then we have a major problem, Houston," wrote Estonian lawmaker Marko Mihkelson, in response to the report.

In a series of hardline statements -- his most extensive comments on the latest U.S.-proposed peace plan to date -- Putin repeated some of Russia's most hardline demands, including that Ukrainian troops must withdraw from territory Moscow claims. Putin ruled out signing any ceasefire deal before Ukrainian troops withdraw.

Even if a peace can be reached, it won’t be easy to solve the problem of Ukrainian civilians languishing in Russian jails. This is one prisoner’s story.

Diplomats and amateur sleuths are chasing questions of means and motive, including who had the capacity to eavesdrop on a call between top officials and who would benefit the most from leaking the conversation?

Russia's state communications watchdog threatened on Friday to block WhatsApp entirely if it fails to comply with Russian law, news agencies reported.