Police used tear gas and batons to disperse hundreds of students, activists and lawmakers who demonstrated in the capital Sanaa to demand the release of Tawakul Abdel-Salam Karman, who was arrested early Sunday.

Interior Minster Mouthar Al-Masri said on state television Sunday that people have the right to express their views but demonstrations, gatherings and marches should be staged within the boundaries of the law.

Karman is a senior member of the opposition Islah Party.

Media rights group Reporters Without Borders on Sunday condemned the arrest of the Yemeni activist and called for her immediate release.

On Sunday, more than 200 journalists staged a march calling for the release of all those arrested during previous demonstrations.

Around 20 people have been arrested over the last 10 days of protests, said Reporters Without Borders.

Karman's family said she was being held at Sanaa's main prison.

Yemeni security officials have confirmed her arrest but have not explained why she was detained.

One of the focuses of the recent protests had been proposals being considered by parliament, despite opposition protests, to extend President Ali Abdullah Saleh's mandate indefinitely.