Police officers carry a wounded participant of an anti-war rally during clashes with pro-Russia demonstrators in Donetsk March 13, 2014 (Photo: Reuters)
Police in eastern Ukraine have detained four people accused of fomenting clashes between rival demonstrators in which one man died, the interior minister said on Friday.
The violence was the worst to hit the ex-Soviet state since the removal of a Moscow-backed president last month.
A 22-year-old man was stabbed to death in Donetsk, the heartland of Ukraine's Russian-speaking coalfield, after pro-Russian protesters clashed with rivals favouring European integration and denouncing Russia's incursion into Crimea. Four of 29 people treated for injuries remained in hospital.
The right-wing party Svoboda, hostile to Russian policy, said the dead man was one of its local activists.
Journalists saw pro-Russian demonstrators throw eggs, smoke bombs and other missiles and break through a police cordon to beat their opponents with batons. Organisers of the pro-Russia protest said their supporters were also attacked.
"The first four organisers and ringleaders of the mass disorders were found and detained during the night," Interior Minister Arsen Avakov said on his Facebook page.
"An investigation is continuing. Given the initial evidence overnight, these detentions are only the beginning. We will not go easy on bandits with knives ... An investigation into police actions during these events will also proceed."
Donetsk, a city of a million, was calm on Friday morning.
Ukrainian officials have accused Russia of supporting groups in the Donetsk region which favour rule from Moscow and of sending militants over the border.
Three weeks ago, about 100 people were killed in the capital Kiev, many of them by police gunfire, in clashes that prompted the flight of Moscow-backed president Viktor Yanukovich.
Yanukovich triggered the protests in November by rejecting a trade deal with the European Union in favour of economic aid from Russia. The Kremlin says its intervention in favour of ethnic Russians in Crimea was prompted by Yanukovich's removal in what it describes as a coup staged by right-wing nationalists.