According to reports, fighting broke out in Ukraine’s second-largest city, Kharkiv, on Sunday when Russian soldiers pushed in from the outskirts.

As per sources, the Kharkiv attack and midnight strikes in Kyiv and other Ukrainian cities widened the Russian invasion that started on Thursday.

Kharkiv, Ukraine’s second-largest city, is just around 12 miles away from the Russian border, some 480 miles east of Kyiv.

According to the BBC, the city has a population of roughly 1.4 million, which is nearly half the size of Kyiv, Ukraine’s Capital.

The Russian assault into Ukraine started Thursday, but Russian forces stayed outside the city of Kharkiv until Sunday, according to the AP.

Civilians have been told to remain in their houses by Kharkiv regional administration chief Oleh Sinehubov, who stated Ukrainian forces were involved in combat against Russians within the city.

At least one residential building in Kharkiv was shelled and Russian military vehicles were seen on the streets according to videos uploaded on social media.

The Russian military blew up the gas pipeline in the Ukrainian city of Kharkiv early Sunday, according to the Ukraine government’s Telegram channel.

Kharkiv developments were one of a series of events that looked to shift the conflict into new territory overnight and on Sunday, according to the AP. In the Kyiv region, the news agency reports that several of the most recent attacks also targeted petroleum facilities.

Russian forces attacked Okhtyrka, Ukraine on Friday, killing at least six people, including a 7-year-old child, according to reports from the BBC.

In all, 240 civilians have been injured, with 64 of them dead, according to a United Nations official.

Russian President Vladimir Putin was reportedly “furious” that the invasion wasn’t proceeding as smoothly as he had anticipated, which led to the appearance of stepped-up attacks. In a tweet, former Estonian defense commander and European Parliament member Riho Terras stated that a Ukrainian intelligence assessment showed that Putin was thought to have anticipated swift triumph, but that Russian soldiers had instead met intense opposition from Ukrainian military and civilians.