The Union home ministry has sought a report from the Uttar Pradesh government on violence in Gorakhpur and some other districts.
Arsonists had torched vehicles and set ablaze a passenger train and several Bharatiya Janata Party leaders were on Wednesday detained on their way to the violence-hit areas.
Authorities did not relax the curfew in the areas and a top police officer was transferred.
Movement of trains on the metre gauge section between Gorakhpur and Gonda on the North Eastern Railway was cancelled after some unidentified elements set ablaze a passenger train at Tulsipur in Balrampur district late on Tuesday night, police sources said in Lucknow.
Two buses and some hutments of members of a particular community were also set on fire in Behrampur in the wee hours on Wednesday, they said.
Hindu Yuva Vahini activists allegedly set on fire an ambulance and tried to burn Varanasi-bound Godan Express at Mau, the sources said.
Violence had erupted on Monday after the arrest of local BJP MP Yogi Adityanath.
Tension prevailed in Basti town, neighbouring Gorakhpur, after some persons set on fire a buried tazia at Karbala late on Tuesday night, they said.
Taking a serious view of the developments, the Uttar Pradesh government transferred Inspector-General of Police (Gorakhpur) Vinay Verma.
BJP leaders -- former union minister Santosh Gangwar, Dharmendra Deo and Satyaprakash Ahluwalia -- sent to Gorakhpur by the BJP central leadership, were arrested from the Gorakhpur-bound Vaishali Express, a report from Barabanki said.
With no relaxation in curfew in Gorakhnath, Kotwali, Rajghat and Tiwaripur, new SSP S K Bhagat warned that those found indulging in violence would be arrested under the National Security Act.