The events in St. Petersburg provoked public indignation and a series of massive strikes that spread quickly throughout the industrial centers of the Russian Empire. Polish socialists—both the PPS and the SDKPiL—called for a general strike. By the end of January 1905, over 400,000 workers in Russian Poland were on strike (see Revolution in the Kingdom of Poland (1905–1907)). Half of European Russia's industrial workers went on strike in 1905, and 93.2% in Poland. There were also strikes in Finland and the Baltic coast. In Riga, 130 protesters were killed on , and in Warsaw a few days later over 100 strikers were shot on the streets. By February, there were strikes in the Caucasus, and by April, in the Urals and beyond. In March, all higher academic institutions were forcibly closed for the remainder of the year, adding radical students to the striking workers. A strike by railway workers on quickly developed into a general strike in Saint Petersburg and Moscow. This prompted the setting up of the short-lived Saint Petersburg Soviet of Workers' Delegates, an admixture of Bolsheviks and Mensheviks headed by Khrustalev-Nossar and despite the Iskra split would see the likes of Julius Martov and Georgi Plekhanov spar with Lenin. Leon Trotsky, who felt a strong connection to the Bolsheviki, had not given up a compromise but spearheaded strike action in over 200 factories. By , over 2 million workers were on strike and there were almost no active railways in all of Russia. Growing inter-ethnic confrontation throughout the Caucasus resulted in Armenian–Tatar massacres, heavily damaging the cities and the Baku oilfields.