Ukrainian forces have reportedly been dealing with Starlink outages as they try to take back Russian-occupied areas. Some of the outages, which are said to have caused a severe loss of communication over the last several weeks, occurred as troops broke through the frontline into territory controlled by Russia as well as during battles, a Ukraine government official told The Financial Times.

The cause of the apparent outages are not yet known. Engadget has contacted Starlink owner SpaceX for comment.

Starlink outages were reported in the four regions that Russia annexed last month following referendums, the legitimacy of which have been disputed. As the Financial Times notes, there’s a significant Ukrainian counteroffensive in those areas.

Some terminals are said to have not been working in areas near Khariv, which Ukraine has almost entirely liberated, amid a push into Luhansk, one of the regions that Russia has claimed. However, military officials claimed this week that Starlink terminals were working in freshly liberated areas east of Izyum and in southern Kherson, according to the report.

Ukrainian troops have been using the terminals to stay in contact, operate drones and receive intelligence while stationed in parts of the country that don’t have other secure networking options. Soon after Russia’s invasion, SpaceX, with the help of American taxpayers, sent thousands of Starlink terminals to Ukraine for both military and civilian use.

SpaceX CEO Elon Musk warned Ukrainians to exercise caution while using Starlink. Researchers pointed out that Russia may be able to use signals from the terminals for targeting purposes. Meanwhile, Musk this week caused anger and concern in Ukraine and among the country’s allies when he suggested that referendums should be held to determine the Russia-Ukraine border. He also claimed SpaceX has spent $80 million to support Ukraine through Starlink.