International trade unions are urging Egypt to release at least seven labor leaders they say have been unjustly imprisoned recently on terrorism-related charges.

The Brussels-based International Trade Union Confederation, and Public Services International, which represent over 200 million workers worldwide, said Wednesday they sent a letter to President Abdel-Fattah el-Sissi last week.

They say that the blocking of legitimate sit-ins and strike action, as well as the arrest of trade unionists on security and anti-terrorism grounds, are a violation of the principle of freedom of association enshrined in the constitution and international treaties of which Egypt is a signatory.

The unions mentioned Tarek Moustafa Ke'eib, president of the Real Estate Taxes employees' trade union in Kafr el-Sheikh province, who is currently detained with a hearing scheduled for Oct. 2.