An armed attack on a U.S. convoy in southeastern Nigeria on Tuesday killed four people, including no Americans, according to local police and a White House official.
"The convoy did not include any U.S. citizen," police spokesman Ekinga Tuchukwu said, adding that the gunmen "killed two members of the mobile police force and two members of the consulate" before burning their car.
The attack took place on Tuesday "at 15:30 (14:30 GMT)" in Ogbaru province, police said.
Tuchukwu said joint security units had been deployed at the site, but the gunmen managed to kidnap two police officers and a driver.
He said in a statement that a "search and rescue operation" had been launched as a result.
In Washington, National Security Council spokesman John Kirby confirmed that a U.S. convoy in Nigeria was attacked that did not result in any U.S. citizen being injured.
The US State Department also confirmed the attack. A ministry spokesman said: "Members of the US mission in Nigeria are involved in the investigation of Nigerian security services."
"The safety of our personnel is always our top priority, and we take the utmost precautions when organizing field trips," he said.
Separatists are active in the area, who have stepped up attacks in recent years, usually targeting police or government buildings.
Nigerian officials attribute the attacks to the Biafra Indigenous Peoples' Independence Movement (MINU), which they describe as a terrorist organization, with its military wing, the Eastern Security Network.