Air raid sirens blared across Ukraine on Tuesday morning for the second straight day of retaliatory missile attacks by Russia for Saturday's explosion on a bridge connecting Crimea and Russia.

Air raid warnings were issued for the capital Kyiv and other places shortly before 8:00 a.m. They were later expanded nationwide, including the western city of Lviv. The warnings have been canceled for most of the cities including Kyiv as of 7:30 p.m. Japan time.

The Ukrainian government is urging the public to stay in shelters.

The governor of the southeastern region of Zaporizhzhia, Oleksandr Starukh, said in a social media post on Tuesday that 12 Russian missiles hit the city, and at least one person was confirmed dead.

Russia's Defence Ministry said on Tuesday that the country's forces attacked Ukraine's command posts and energy infrastructure from the air and sea.

The Ukrainian State Emergency Service says 19 people were killed and 105 others were injured in Monday's attacks.

Russian President Vladimir Putin told a meeting of his country's security council that the bridge blast was an act of sabotage by Ukrainians, and that Russia has retaliated for the attack.

The Institute for the Study of War, a US think tank, says cruise missiles and drones, some Iranian made, were used in Monday's attacks. It says Russian forces launched missiles from a western Russian base, as well as the Caspian Sea and the Black Sea, and drones from Crimea and Belarus.

The institute says Putin ordered the attacks "in part to curry favor with the Russian pro-war nationalist camp."

Putin said on Monday that "in the event of more attempts to stage terrorist attacks on our territory, Russia's response will be harsh and commensurate with the threats posed to the Russian Federation."

The institute says this statement suggests "Putin intends to continue climbing the escalation ladder rung by rung and cautiously rather than jumping to more dramatic measures such as the use of nuclear weapons."