Riot police have fired teargas and water cannons, beaten demonstrators and arrested union leaders, activists and journalists in an attempt to stop pro-democracy protests in Swaziland, Africa's last absolute monarchy.

Simantele Mmema, spokeswoman for the Swaziland National Association of Teachers, told the Associated Press that riot police dispersed more than 1,000 workers who were singing and chanting in a teacher training centre.

Earlier, more than 150 paramilitary police surrounded Freedom Square in the commercial capital, Manzini, separating any groups of two or more people. Buses approaching the city were stopped by police, with passengers held under guard or driven back in the opposite direction. At least seven labour leaders were arrested early in the morning, while several foreign journalists were detained. Five activists were arrested on Monday evening ahead of the planned march, which had been banned by the authorities.