PRISTINA, Serbia, Oct 5 (Reuters) - Police in Kosovo have arrested two of the seven men who escaped from a top-security prison in August but the most dangerous fugitives are still on the run, officials said. The seven inmates, including convicted murderers, escaped from Dubrava prison, in the west of the United Nations-run province, with the help of their guards. Among four accomplices also arrested was an officer in Kosovo's police force, the sister of one of the fugitives. She was detained at Pristina airport while trying to flee. "The officer provided her brother with police uniforms," Rrahman Sylejmani of the Crime Unit told reporters. One of those captured is suspected of having committed a robbery last month, disguised as a policeman. The five who are still on the run include Ramadan Shyti, wanted on murder and terrorism charges in neighbouring Macedonia, and Lirim Jakupi, believed to be a leader of the shadowy Albanian National Army. Police also raided an apartment rented by the gang and found automatic weapons, pistols, ammunition and passports. That was proof, Sylejmani said, "they were planning other attacks". The United Nations, which has around 1,300 police officers in the province, has no direct role in running Dubrava prison. But the escape embarrassed the mission and the 16,000-strong NATO-led peace force in Kosovo. The breakaway Serbian province has been a U.N. protectorate for the past eight years, since NATO bombed Serbia to drive out Serb forces and halt the killing and expulsion of ethnic Albanians in a two-year war against guerrillas. Ninety percent of Kosovo's 2 million people are ethnic Albanians, who want independence.