MOSCOW (AFP) ― President Vladimir Putin on Monday ridiculed the Ukrainian army as NATO’s “foreign legion,” ignoring Western pressure on the Kremlin to rein in a pro-Russian insurgency that has gone on the offensive across eastern Ukraine.

Putin’s comments came as an emergency meeting of the Western alliance’s NATO-Ukraine Commission was called to discuss a surge in fighting that has led to a spate of civilian casualties and rapidly growing pressure on Ukraine’s troubled military.

Another 12 people were reported killed Monday, including seven Ukrainian soldiers, as Kiev accused the pro-Russian rebels of firing more than 100 times over the past day on both military positions and civilian areas.

Fighting was said to be particularly intense near the government-held city of Debaltseve, halfway between the rebel strongholds of Donetsk and Lugansk, where the military said separatists were attacking with tanks and multiple rocket launchers.

Western governments and Kiev accuse Moscow of arming, training and fighting alongside the rebels. Russia denies any direct involvement, although repeated sightings of large numbers of sophisticated heavy weapons being used against Ukrainian forces has stretched the credibility of those denials.

Putin, on a visit to Saint Petersburg, claimed Ukrainian men wanted to flee to Russia because they did not want to become “cannon fodder” in an army that he described as mostly “volunteer nationalist battalions.”

“In essence, this is not an army, this is a foreign legion ― in this particular case NATO’s foreign legion, which of course does not pursue the objective of serving Ukraine’s national interests,” Putin said.

He said the aim was “Russia’s containment” and that the Ukrainian government was not interested in a peaceful settlement.

NATO head Jens Stoltenberg later dismissed the comments as “nonsense”.

“The foreign forces in Ukraine are Russian,” Stoltenberg told a press conference at the alliance’s headquarters in Brussels. “So I think that is in a way the problem, that there are Russian fores in Ukraine and that Russia backs the separatists with equipment. And we have seen a substantial increase in the flow of equipment from Russia to the separatists in Ukraine.”

The unravelling of a September truce deal has picked up pace in the last few days, with the main rebel leader in the Donetsk region last week announcing he would no longer take part in peace talks and planned to seize more territory.

On Saturday, a barrage of rocket fire killed 30 people in a residential area of Mariupol, the last major city in the country’s two separatist provinces still controlled by Kiev.

Monitors from the Organization for Security and Co-operation in Europe said the rockets were fired from the direction of separatist-held areas, although rebels distanced themselves from the attack.

The leader of the self-proclaimed Donetsk People’s Republic, Alexander Zakharchenko, initially claimed Saturday to have launched an offensive aimed at taking Mariupol, but as the extent of the bloodshed became apparent he denied ordering an assault on the industrial port on the Sea of Azov. Mariupol remained calm on Monday.

Russia is already under heavy Western sanctions over its alleged actions in Ukraine and the recent violence has led to threats of new measures against Moscow.

U.S. President Barack Obama vowed to ramp up pressure on the Kremlin after Saturday’s slaughter in Mariupol. Analysts say that if rebel forces did capture the city, they would then be close to creating a land corridor linking Russia to the Black Sea peninsula of Crimea, another Ukrainian province that Moscow annexed last March.

Obama said he would look at all options ― short of military intervention ― to restrain Putin’s alleged campaign to cripple Ukraine’s pro-Western leadership by stripping away their country’s vital eastern industrial base.

In a call to Putin on Sunday, German Chancellor Angela Merkel urged the Russian president to pressure the separatists to end the upsurge in violence.

Ukrainian President Petro Poroshenko told his top generals that he had asked the European Union to tighten its own sanctions on Russia when EU foreign ministers hold a special session in Brussels on Thursday.

The U.N. Security Council also planned to hold a special meeting at 2000 GMT on Monday on the violence that has rocked eastern Ukraine in recent days.

Both sides on the ground accuse the other of endangering civilians by firing into built-up areas.

Pro-Kiev officials still functioning in the two separatist regions said they were planning evacuations of children from areas considered to be in immediate danger.