Two Spanish aid workers kidnapped from Kenya's Dadaab refugee camp are believed to have been taken across the border into lawless Somalia, police said Friday. The two women, working as logisticians for the aid agency Medecins Sans Frontieres (MSF, Doctors Without Borders), were seized Thursday by gunmen that police say were Somali Islamist Shebab rebels. "There are all indications that they are on the other side (of the border)," regional police chief Leo Nyongesa told AFP. Fierce fighting was reported in a town just inside Somalia on Thursday between Al-Qaeda linked Shebab militants and other rival Somali militia groups. Despite the likelihood the kidnappers are now in Somalia, police said they would continue the search in Kenya on Friday with the support of a helicopter. "We have not found them, but the search is still going on. We will resume the search this morning both on the ground and in the air," he added. The Kenyan driver of the aid workers was shot and wounded by the gunmen, who then drove with the women towards the Somali border. The four-wheel drive vehicle was found late Thursday by police in the Dadajabula area, less than 20 kilometers (12 miles) from the Somali border, and 40 kilometres (25 miles) from where the women were seized. "We suspect they were unable to proceed with it due to poor terrains because it was raining," Nyongesa added. In Madrid, the foreign ministry said "The Spanish embassy in Kenya is working on the case." It declined to name the women. Kenya is still reeling from the kidnappings of a French and British national recently from coastal regions by Somali gunmen that dealt a blow to its key tourism sector. Earlier this month, Frenchwoman Marie Dedieu was seized from her beachfront home in Kenya's popular tourist destination of Lamu, and taken to Somalia. Gunmen also captured British holidaymaker Judith Tebbutt from Lamu district and killed her husband. No demands have been made public by the gunmen for the release of the hostages. Dadaab, the world's largest refugee complex, is home to some 450,000 refugees, most of whom have come from Somalia, fleeing drought and war. "We strongly condemn this attack", said Jose Antonio Bastos, the president of MSF-Spain. "MSF is in contact with all the relevant authorities and is doing all it can to ensure the swift and safe return of our colleagues." The head of the UN refugees agency slammed the kidnapping as "unacceptable". "These Medecins Sans Frontieres colleagues were working to rescue lives," Antonio Guterres, UN High Commissioner for Refugees, said in a statement. "It is wholly unacceptable that they should be made targets for kidnap. I appeal to those responsible to facilitate their immediate and safe return." Kenyan authorities have on several occasions expressed fears that Islamist extremists would infiltrate the Dadaab camps from Somalia, as the border lies barely 100 kilometres (60 miles) away. Policing the sprawling camps is extremely difficult, Kenyan authorities say. The camps have seen a huge influx of people this year -- more than 7,500 people have arrived in the crowded complex of rag, tin and plastic huts this month alone. The exodus hasbeen sparked by a severe drought that has affected more than 13 million people across the Horn of Africa, hitting Somalia especially hard with the UN declaring famine in several southern regions. The Al-Qaeda-linked Shebab control much of southern Somalia, and recently fought heavy battles with local militia backed by Kenyan military along the border areas, near Dadaab.