* Dadaab is the world's largest refugee camp
* Several attacks in area since Kenya sent troops into Somalia (Adds detail, background)
GARISSA, Kenya, Dec 5 (Reuters) - An explosion killed one Kenyan police officer and wounded three on Monday at the Dadaab refugee complex in the north of the country near Somalia, provincial police commander Leo Nyongesa said.
He said the blast occurred in the Ifo refugee camp, part of the Dadaab facility in North Eastern province that is home to more than 400,000 Somalis. The Kenya Red Cross confirmed the casualties.
The officers were in a convoy of police cars escorting United Nations officials to the camp. The blast took place when they stepped out of their car, Nyongesa said.
Kenya sent troops across the border into Somalia in October to crush the al Qaeda-affiliated al Shabaab rebels it blames for attacks on its security forces and tourists inside Kenya, and the kidnap of two Spanish aid workers from Dadaab.
Since then, there has been a string of attacks in the area. A remote-controlled bomb hit a police car in another part of the Dadaab complex on Nov. 15 and on Nov. 5 a U.N. convoy struck a bomb buried in the camp, but it did not explode.
The attacks in Dadaab, coupled with the kidnappings in October, have forced a number of aid agencies to scale back staff numbers, hitting the provision of aid to those living in the world's biggest refugee camp. (Reporting by Daud Yussuf; Writing by James Macharia; Editing by David Clarke)