A man shouts during a protest in Sana'a as thousands demand for Yemen's president to step down. Image Credit: AFP

Sana'a: Thousands of protesters gathered at Yemen's Sana'a University for the fourth day, demanding that President Ali Abdullah Saleh step down.

The protesters clashed with pro-government demonstrators who hurled stones and wielded clubs.

The crowd of about 3,000 protesters tried to march from Sanaa University to the city centre where Saleh's supporters have been camped since last week, but were prevented by security forces who erected razor wire.

The protesters, mainly students and civil society activists, chanted slogans calling on Saleh, who has been in power for 32 years, to follow the example of Egypt's Hosni Mubarak who was forced out of power on Friday.