Story highlights One of the bombs targets Sheikh Dahiru Bauchi, a Muslim cleric

Another targets Muhammadu Buhari, the former military ruler

Both figures were unharmed

Nigerian President condemns the attack during Ramadan

At least 40 people in northern Nigeria were killed Wednesday in two suicide blasts targeting a renowned Muslim cleric and an opposition politician, prompting a round-the-clock curfew to prevent chaos.

"We have recorded two suicide blasts today in the city, which have killed 40 people," Kaduna State Police Commissioner Umar Shehu said of the blasts that also injured scores of people.

Twenty-five people were killed in the first blast, which targeted the motorcade of Sheikh Dahiru Bauchi, the revered leader of the Tijjaniyya Sufi order in Nigeria, after he left the finale of an annual Koranic conference.

The second blast occurred about two hours later and killed at least 15 people, officials said. It targeted Muhammadu Buhari, the former military ruler and opposition presidential candidate in the 2007 and 2011 elections.

Both targeted figures escaped unhurt.

Nigerian President Goodluck Ebele Jonathan condemned the bombings and "commiserates with all those who were injured in the twin bombings in this holy month of Ramadan, which defy the tenets of Islam," adviser Reuben Abati said.

U.S. State Department spokeswoman Marie Harf said America "deplores today's twin bombings in Kaduna, Nigeria, which targeted Shaykh Dahiru Usman Bauchi, one of the country's most respected Muslim scholars, during the month of Ramadan." She added that reports cited how former head of state Buhari may have also been targeted.

Kaduna Gov. Mukhtar Ramalan Yero imposed a 24-hour curfew on the city of Kuduna "to enable security agencies (to) restore normalcy," spokesman Ahmed Maiyaki said.