Kenyan security officials say their forces will pursue Somali militants across the Kenya-Somali border, following the kidnapping of four Europeans in recent weeks.

Internal Security Minister George Saitoti says Kenya is being threatened with a serious level of terrorism.

Defense Minister Yusuf Haji says Kenyan forces have a right to pursue the militants if Kenya is attacked. He says Kenyan troops will try to push the insurgents as far away from the border as possible.

Reports say large numbers of Kenyan security forces, as well as aircraft and military vehicles, were close to the Somali border on Saturday.

Kenyan police suspect the Somali militant group al-Shabab was behind the abduction Thursday of two Spanish aid workers from a large Somali refugee camp in northern Kenya. Authorities say the kidnappers may have tried to take the workers to Somali territory.

A British tourist and a French woman were recently abducted at Kenyan resorts. Both of those women are being held captive in Somalia.

A driver working with the Spanish aid workers was shot during Thursday's abduction and left behind. An official with Doctors Without Borders told VOA he is in stable condition.