KYIV — Several heavy explosions reverberated across Kyiv at 11 a.m. local time Monday.

They appear to have been caused by Ukrainian air-defense batteries aiming at either Russian aircraft or cruise missiles.

Several trails of smoke heading into the sky could be seen from central Kyiv.

At least two people died and three were hospitalized after a residential building in a suburb of the capital was hit by shelling Monday morning, Ukraine's emergency services said earlier today.

Fifteen people were rescued and 63 evacuated after a shell hit the ninth floor of a residential building in the Obolon district, a northern suburb of Kyiv.

Land corridor

A land corridor has been established between Crimea and Donbas, according to Russian state news agency RIA Novosti.

In its report, the news agency cited the Vice-Premier of Crimea Georgiy Muradov, who is the Permanent Representative of the Republic of Crimea under the President of Russia.

CNN has not been able to independently verify the Russian state media report.

According to RIA, the corridor provides a strategic route connecting Crimea to Mariupol, which is currently surrounded by Russian and Russian-backed separatist troops.

The land corridor would allow troops in Crimea to join forces with Russian-backed rebels in the self-proclaimed Donetsk People's Republic (DPR), as well as giving Russian-backed forces access to key port cities along the Sea of Azov.

The RIA report also called it an "important route" for connecting Crimea to the steel-making capital Mariupol and the industrial Donbas region.

2.5 million refugees

In little over two weeks, millions of Ukrainian refugees have been forced to flee as the brutal Russian invasion of their homeland continues.

The amount of people on the move constitutes "the fastest growing refugee crisis in Europe since World War II," UN Refugee Agency (UNHCR) Commissioner Filippo Grandi said Sunday.

While many residents in the central and eastern portions of the country have relocated to western Ukraine and away from the front lines, more than 2.5 million Ukrainians have left entirely following Russia's invasion on February 24, according to the latest United Nations refugee estimates.

Most of those fleeing Ukraine are women and children. Ukrainian males aged 18 to 60 were banned from leaving after its national government enforced martial law.

With more than 1.6 million Ukrainians crossing into its territory as of Friday, according to UNHCR data, Poland has received by far the most refugees.

Nations directly to the west and south of Ukraine have also accepted large numbers of refugees. Since the invasion, more than 245,000 Ukrainians have entered Hungary, while over 195,000 have fled to Slovakia, according to UNHCR data Friday.

Over 328,000 refugees have arrived in Moldova, the country's Foreign Affairs Minister Nicu Popescu said.

And more than 173,000 have since fled to neighboring Romania, according to UNHCR.

Across Europe, nations including Germany, Austria, Croatia, Estonia, Greece, Ireland, Italy, Lithuania, the Netherlands, Portugal and Sweden have each reported thousands of Ukrainians arriving. — CNN