Three armed men, including two disguised in women's abayas, were killed in a clash with a policeman in the western border town on Haradh on Saturday, a police official said.
Haradh is a main town located on the border with Saudi Arabia.
Policemen stopped a bus carrying four men for inspection at a checkpoint near Haradh, Hajja province, after noticing that two of them were disguising in women's black robes and wearing the face-covering veil (niqab), the Hajja Police Deputy Chief, Colonel Hussein al-Haifi, told Saba.
The suspects later shot at a policeman as he escorted them to the police center in the town on the same bus.
He fired back killing three and injuring one. The policeman and the bus driver were also injured in the shootout, al-Haifi said. They were rushed to a hospital.
Al-Haifi denied reports that the men were affiliated with al-Qaeda.
"Police authorities are still investigating this incident, and have yet to reach any conclusion, and have got no evidence linking them to terrorists," he said.