A short-lived ceasefire in eastern Ukraine apparently collapsed late Saturday when fighting broke out in Mariupol, a port city in the country's southeastern region.
BBC journalist Fergal Keane — who just hours before the shooting began had reported that the ceasefire was holding — tweeted from the scene.
Other witnesses told the Associated Press the fighting included explosions and rocket fire on the eastern edge of the city. Ukrainian troops have established defensive lines against the pro-Russian rebels in that same area.
BBC News producer Will Vernon tweeted a picture that appeared to show an explosion.
Other journalists who tweeted about the violence included Roland Oliphant of The Telegraph, Shaun Walker of The Guardian, and Polish television reporter Wojciech Bojanowski.
The ceasefire began Friday and initially appeared to be holding.
The ceasefire between the Ukrainian government, pro-Russian rebels, and Russia was signed Friday in Belarus. Immediately after it took effect, shelling appeared to stop in eastern Ukraine, the AP reported.