The incident occurred when the express train came on the same track near Khalilabad Railway Station, officials said.
Initial reports said that at least six coaches and the engine of the train were derailed in Sant Kabir Nagar district of Uttar Pradesh, 230 km from the capital Lucknow.
The district administration, involved in the rescue and relief operations said that the number of casualties could be higher.
Senior railway officials have rushed to the spot. According to officials, over 50 people have been admitted to various medical facilities and the casualties could increase further.
"Relief work has begun, there are casualties but exact figure is not yet known", Arunendra Kumar, Chairman of Railway Board told a news agency.
Here are the Helpline numbers: 05222635639, 0522228880, 055512204893
20 feared dead after Gorakhdham Express collides with stationary goods train in UP pic.twitter.com/mKu7UqIW6b— NDTV (@ndtv) May 26, 2014
My heartfelt condolences to the members of the bereaved families. I wish for speedy recovery of those who got injured in the train accident.— Rajnath Singh (@BJPRajnathSingh) May 26, 2014
Modi condoles passengers' death in UP train accident
Prime Minister-designate Narendra Modi on Monday expressed his condolences to the families of those who died in a train accident in Uttar Pradesh and spoke to a top official to "ensure timely assistance to those injured".
"My condolences to families of those who lost their lives in the Gorakhdham express tragedy. Prayers with the injured," tweeted Modi.
"Spoke to the Cabinet Secretary. Asked him to take an overview of the situation & ensure timely assistance to those injured," he added.
Sonia Gandhi expresses grief at loss of lives in train accident
Congress president Sonia Gandhi on Monday expressed grief over the loss of lives in Gorakhdham Express accident and hoped that the Railways was taking all possible steps to help the affected passengers and their families.
"Sonia Gandhi has expressed shock and grief over the unfortunate accident of Gorakhdham Express near Khalilabad in UP today. Anguished at death of passengers, Gandhi extended condolences to the family of the dead and wished a speedy recovery to those injured," the party said in a release.
Gandhi also expressed the hope that railways was taking all steps for relief and safety of the victims and stranded passengers, the party said.