Ukraine began two days of missile tests near Crimea on Thursday - a move that has angered Russia, which has put its air defense forces on high alert and deployed warships in the Black Sea.
The disagreement marks a fresh escalation in tensions between the one-time allies, whose relations collapsed in 2014 after Russia seized Crimea and backed pro-Russian separatists fighting in eastern Ukraine.
Volodymyr Kryzhanovsky, a Ukrainian military official, said the exercises, which are taking place in Ukraine's southern Kherson region bordering Crimea, had begun and that everything was going smoothly.
"The tests are being carried out in accordance with international law," Kryzhanovsky told the 112 TV channel.
The exercises, which will run from Dec. 1-2, were taking place at least 30 kilometers (18.64 miles) from Crimean air space, he said.
"Therefore it would be wrong to reproach Ukraine," he said.
Moscow has responded by putting its land-based and ship-borne air defense forces in Crimea on higher alert and a Russian military source has accused Ukraine of trying to create a "nervous situation."
Warships from Russia's Black Sea Fleet took up position off Crimea's western coastline on Thursday to help strengthen the peninsula's air defenses, a Crimean military source told the RIA news agency.
"The ships' air defense units have been put on a higher state of alert," said the source. "Together with land-based air defense units on the peninsula, the ships have thrown up a practically impenetrable shield against the enemy's rockets."
Ukraine says the aim of the tests is to bolster its defense capabilities.
Kremlin spokesman Dmitry Peskov told reporters on Wednesday that he did not know whether President Vladimir Putin had ordered the defense ministry to prepare a potential military response to the Ukrainian tests.
He was responding to a question about Ukrainian media reports which said that the Russian Defense Ministry had told Ukraine's military envoy that Moscow would shoot down any missiles and destroy their launchers if Kiev test-fired missiles in the air space near Crimea.
"In the Kremlin we wouldn't want to see any actions by the Ukrainian side that breached international law and that might create dangerous conditions for international flights over the territory of Russia and adjacent regions," said Peskov.
Kryzhanovsky said the Ukrainian military was ready for "any developments".
Russia held large-scale war games across its southern military district in September, including Crimea.