Russia fired a wave of attack drones and missiles at Ukraine on Monday and Tuesday, killing at least 11 people and battering the country's already weakened energy grid.

NATO members reaffirmed their commitment to "stepping up their military aid to Ukraine", NATO chief Jens Stoltenberg said, following the meeting of ambassadors with Ukrainian officials at Kyiv's request.

"We must continue to provide Ukraine with the equipment and munitions it needs to defend itself against Russia's invasion. This is vital for Ukraine's ability to stay in the fight," Stoltenberg said in a statement.

Several NATO countries also called for lifting restrictions on Kyiv's use of weapons supplied by Western allies, especially long-range missiles, to help Ukraine better defend itself against deadly strikes, a diplomatic source said.

Ukrainian Defence Minister Rustem Umerov "briefed allies" about the situation on the ground, NATO said.

The Ukrainian army is struggling in the east, where Russian troops have been steadily advancing for several months.

The Russian army has captured several towns and villages in recent days, even as Moscow scrambles to fight off a Ukrainian counterattack into its western Kursk region.

President Volodymyr Zelensky has called for European air forces to help Kyiv down drones and missiles in the future.

"In our various regions of Ukraine, we could do much more to protect lives if the aviation of our European neighbours worked together with our F-16s and together with our air defence," Zelensky said.

The air attacks on Ukraine are some of the largest in recent weeks, with 15 Ukrainian regions targeted by a total of 236 missiles and drones, Kyiv said, of which it claimed it shot down 201.