Nigerian forces have killed a suspected Islamist militant during an operation that targeted suspects believed to be linked to an attack on Christian worshippers Sunday.

Officials say a military task force stormed a hideout early Tuesday in the northern city of Kano. Soldiers killed one suspect and arrested three women, while another suspect escaped. The soldiers also found weapons and explosives.

On Sunday, gunmen killed at least 15 people in an assault on a Kano theater used for church services at Bayero University.

In a statement Tuesday, U.S. Secretary of State Hillary Clinton expressed U.S. concern about attacks on churches, news media and government installations in Nigeria. Clinton says the U.S. strongly condemns attempts to inflame Christian-Muslim tensions in Nigeria, and supports those who recognize Nigeria's ethnic and religious diversity as one of the country's strengths.

No group has claimed responsibility for Sunday's attack, which resembled others carried out by the Islamic militant group Boko Haram.

Boko Haram, whose name means “Western education is a sin” in the Hausa language, is trying to turn Nigeria into an Islamic state. Human Rights Watch says the group has killed more than 1,000 people since 2009.