Police and emergency officials in Nigeria say explosions have struck two churches in the northern part of the African country.

What appear to be militant attacks occurred in different sections of the city of Zaria. There are no immediate reports of casualties.

Authorities have not publicly said who might be responsible, but the militant group Boko Haram has targeted churches in the past, especially those in the northern region of Nigeria. The group has said it wants to establish an Islamic state in the north and does not recognize the government or the country's constitution.

The country of 150 million is about evenly divided between Muslims, who mostly live in the north, and Christians who dominate in the south.