Suspected Somali gunmen have kidnapped two international aid workers in the world's largest refugee camp in Kenya.
The incident triggered a police pursuit by land and air after a spate of similar attacks on Kenya's coastal resorts.
The gunmen hijacked the workers' vehicle and shot the driver in the neck, according to Baijo Mohamed, a youth leader in the Dadaab refuge camp.
Regional police chief Leo Nyongesa said he believes the attackers came from Somalia because that was the direction they fled after the attack. The Dadaab camp lies about 50 miles from the border.
"We are following them by the road and air. We have closed the borders. We are tracking them down," Mr Nyongesa said.
The two international aid workers from Doctors Without Borders were likely to be Europeans, officials said.
A Doctors Without Borders spokeswoman said she could not immediately comment.
A security official in Nairobi said that initial reports indicated two Kenyans also were abducted. He later said that report was inaccurate.
The attack on Thursday follows the kidnappings of a British tourist and a French woman from Kenyan resorts near the Somali border and would appear to represent the escalation of a new tactic by Somali militants or pirates.
Pirates have long sought ransoms in the millions of dollars for high-value hostages typically taken at sea.