U.S. President Joe Biden's latest security assistance package for Ukraine includes surveillance drones, and for the first time, mine-resistant vehicles, a senior U.S. defense official said on Friday.

Since Russian troops poured over the Ukrainian border in February in what Russian President Vladimir Putin termed a "special military operation," the conflict has settled into a war of attrition fought primarily in the east and south of Ukraine.

The official, speaking on the condition of anonymity, said the package would be valued at $775 million and also include additional ammunition and 16 105mm howitzer systems.

The package would include 15 Scan Eagle surveillance drones, 40 MaxxPro MRAP (mine resistant ambush protected vehicles) and about 1,000 Javelin anti-tank missiles.

While this is the first time the United States is providing Scan Eagle drones, another country has provided them to Ukraine in the past, the official said, without elaborating.

Reuters first reported on the package on Thursday.

This would bring the total U.S. military aid sent to Ukraine since the Feb. 24 invasion by Russia to $10.6 billion.

Explosions erupted overnight near military bases deep in Russian-held areas of Ukraine and Russia itself, an apparent display of Kyiv's rapidly growing ability to wreak havoc on Moscow's logistics far from front lines.

Since last month, Ukraine has been fielding advanced rockets supplied by the West to strike behind Russian lines. The overnight explosions in Crimea and Belgorod were beyond the range of ammunition Western countries have acknowledged sending so far.

In recent days, Kyiv has been issuing warnings to Russians, for whom Crimea has become a popular summer holiday destination, that nowhere on the peninsula is safe as long as it is occupied.