Abuja, April 20 (IANS) At least 17 people have been killed in different parts of northwest Nigeria after the presidential election, medical officers said.

"We have at least five verified deaths and many more injuries," James Mahadi, the chief medical director of the Gombe State Specialist Hospital, told Xinhua.

The acting head of the Federal Medical Centre in Gombe, Ali Misheliza, said 12 people have been confirmed dead, while 71 injured were being taken care off.

Violence spread Tuesday in northern Nigeria as youths protested the results of Saturday's presidential election being released state-by-state.

Curfew has been imposed in Kano and Kaduna, densely populated cities in northwestern Nigeria.

Riots also spread to the capital city of Abuja, Lafia, Taraba and Kaduna.

According to reports, the residence of Namadi Sambo, the country's vice president, was torched by a mob.

Churches and other public buildings were also burnt in Kaduna.

Rioters smashed cars, leading to the closure of banks and other business premises, including the largest market, in Abuja.

Local and international observers adjudged the election free and fair.