Lebanese supporters of a Christian politician are protesting in downtown Beirut and have clashed with troops who blocked them from reaching the government building where a Cabinet session is underway.

Leader of the Free Patriotic Movement Michel Aoun called for Thursday's demonstrations following a dispute over security appointments in the government.

Aoun insists that the government should make the appointments a priority while government officials say only regular items would be on the agenda.

Lebanon has been without a president since May 2014 and Aoun has accused Prime Minister Tammam Salam of taking advantage of the presidential vacuum and running the country as if he were president.

Lebanon is the only country in the Arab world where the post of the president is held by a Christian.