It is by no means unusual for shelling to take place in the Donbas region, which has effectively been in a state of civil war for nearly eight years now. The area includes two self-declared republics that broke away following the pro-European 2014 Ukrainian revolution.

However, local observers also told Fortune that the scale of the violence was unusually high. The attacks—which included the reported shelling of a kindergarten in a Ukraine-controlled enclave within the so-called Luhansk People’s Republic—also come at a time of extraordinary tension.

Not only are there more than 170,000 Russian troops massed at the Ukrainian border, but the Russian parliament earlier this week asked President Vladimir Putin to recognize the Luhansk and Donetsk people’s republics. Such a step would effectively scrap the never-entirely-observed cease-fire in the region, and Putin is thus far holding back. But on Tuesday he repeated his claim that Russian speakers face “genocide” in Donbas, and some, including the U.S., fear he will use reports of violence against separatists as a justification for invasion.

“It is not typical. It looks a lot like a provocation,” an unnamed Ukrainian government source told Reuters.

Pro-Russian separatists claim Ukraine’s armed forces violated the 2015 Minsk peace agreements by breaching the cease-fire with prohibited heavy weapons. Russian media is also taking this line, with the state-owned Tass news agency reporting late morning that the Ukrainian side had violated the cease-fire 15 times since the start of the day, with weapons including anti-tank missiles. Kremlin spokesman Dmitry Peskov characterized the situation as an intensification and a provocation from the Ukrainian side.

However, Ukraine says rebel forces used heavy weapons to attack the village of Stanytsia Luhanska, which is under Ukrainian control. As documented by the humanitarian NGO Proliska, which is monitoring the conflict zone, one of the shells struck a kindergarten, leaving two employees with shell shock—but not injuring any of the children who were there. Proliska and journalists have also reported shelling by pro-Russian forces against the inhabitants of the Ukrainian town of Mariinka.

“We call on all partners to swiftly condemn this severe violation of Minsk agreements by Russia amid an already tense security situation,” tweeted Ukrainian Foreign Minister Dmytro Kuleba.

Russia says it is pulling back some forces from Crimea, the region it illegally annexed in 2014, but the U.S. and NATO insist there is no significant drawdown underway, and that in fact more troops are heading to the border. In response, Moscow has accused the U.S. of “anti-Russian hysteria.”