South Africa's umbrella trade union said on Wednesday that South African police had opened fire at union protesters seeking to blockade a border crossing into Swaziland in a pro-democracy demonstration, Reuters reported. The Congress of South African Trade Unions (COSATU) said several people were wounded in the incident at the Matsomo border post in Mpumalanga province and that 20 others had been arrested. Police were not immediately available for comment. "COSATU is appalled by the conduct of police and will be taking this up with the utmost urgency with the government and the SAPS leadership," the union said in a statement. COSATU officials also said four senior trade union leaders had been arrested at another border post with Swaziland as COSATU joined Swazi pro-democracy groups in an effort to shut down the border to press demands for political reform in the tiny African kingdom.