Ukraine plans to open a humanitarian corridor for civilians to leave Mariupol, the besieged south-eastern city where Russia this week began a bombing campaign targeting the city’s Azovstal steelworks.

The government secured agreement on a corridor to bring civilians out of the city from 2pm, Iryna Vereshchuk, Ukraine’s deputy prime minister, said on Wednesday.

“Given the catastrophic humanitarian situation in Mariupol, it is in this direction that we will focus our efforts today,” Vereshchuk wrote on the Telegram social media platform. “We managed to agree in advance on a humanitarian corridor for women, children and the elderly.”

She said that changes might occur to the path of the corridor “due to the very difficult security situation”.

Several attempts to evacuate civilians from the city have collapsed because of mistrust between the warring sides since Russian troops encircled and bombarded the city and cut off power, water, heat and other basic services in early March. It was not immediately clear whether the corridor announced by Vereshchuk had Russian support.

According to Ukrainian officials, Russia has begun using bunker-busting bombs on and near the grounds of the Azovstal steelworks, the last area of the city under Ukrainian military control. They said civilians, including children, were hiding from the bombing alongside the fighters in shelters beneath the sprawling complex, one of Europe’s largest steelworks.

Ukraine’s military said in an update on combat operations on Wednesday that the Russians’ main efforts were “focused on capturing the city of Mariupol, continuing the assault in the area of the Azovstal plant”.

Serhiy Volyna, commander of Ukraine’s 36th marine brigade in Mariupol, among the last Ukrainian troops in the city, released a video on Tuesday in which he pleaded for international action to “save Mariupol”. He included the hashtags #PopeActNow and #KidsOfCatacombs.

Ukrainian military claims have not been independently verified.