NAIROBI (AP) - Militants believed to be from Somalia's Islamic extremist group al-Shabab killed at least four police officers in an attack on a police post near the Somalia border, an official said Saturday.

About 40 armed extremists on Friday night raided a police post in Galmagalla village, a remote area that has poor communications infrastructure, said Mr Rashid Khattor, the commissioner for Garissa county in Kenya's north east.

"We have alerted all units of our security personnel including (the Kenyan military) to immediately respond to the attack," he said.

He said a local chief and a school teacher were wounded in the cross-border attack.

Somalia's Islamic extremist network al-Shabab claimed responsibility in updates on Twitter, saying its fighters killed five police officers and seized dozens of weapons and communication equipment. The militants claimed they had burned down the police post before retreating back to Somali territory.

Al-Shabab has staged many attacks inside Kenya in retaliation for the Kenyan government's decision in Oct 2011 to send troops into Somalia to battle the rebels. The Kenyan government sent troops there after several cross-border attacks and kidnappings of foreign tourists.

Although the Al-Qaeda-linked militants have been greatly weakened since African Union troops pushed them out of Mogadishu, they are still able to operate in remote parts of Somalia and launch targeted attacks that kill and wound many civilians.