Two pan-Arab news channels said the Yemeni authorities had seized broadcasting equipment from their Sanaa bureaux by force because of their coverage of the growing unrest in Yemen's south.

A government official told state media that Qatar-based Al Jazeera television and the Saudi-owned channel Al Arabiya did not have proper authorisation for the equipment seized, and that it would be returned to them eventually.

Al Jazeera said Yemeni security forces had stormed its office in Sanaa after being warned over its coverage of a southern secessionist movement on which the government recently launched a major crackdown.

An official had telephoned Al Jazeera's office earlier on Thursday, saying measures would be taken if the channel covered a meeting of southern opposition leaders, Murad Hashim, the head of Al Jazeera's Sanaa bureau said on the channel's website.

Al Arabiya also reported that some of its broadcasting equipment had been confiscated by police on Thursday. Its bureau chief was questioned for two hours but then released, Nasser al-Sarami, head of media at Al Arabiya told Reuters.

'They are concerned about the way we cover what is going on in the south. They didn't give us a reason, but we believe this is the link,' Sarami said.

Thousands gathered for demonstrations across Yemen on Thursday to demand an easing of the crackdown in the south. Two people were shot dead as security forces tried to quash a separatist protest in a southern province.

Also on Thursday, Yemeni forces launched an attack to recapture a government building occupied by separatists in the south of the country, setting off a gunfight that killed two people.

Under international pressure to quell domestic unrest and focus its sights on al Qaeda, Yemen earlier this week offered to hold talks with southern separatists and hear their grievances.

The offer by President Ali Abdullah Saleh followed an escalation of violence on both sides in southern Yemen which left a trail of dead and wounded in recent weeks while insurgent violence elsewhere in the country has faded.

Thursday's demonstrators were calling for the military to withdraw from southern cities and for the government to halt a sweeping campaign of arrests.

Satellite television stations Al Jazeera and Al Arabiya are among the most widely watched news channels in the Arab world.

Al Arabiya has around 200 million viewers across the globe, Sarami told Reuters. – Reuters