"Enough being in power for (over) 30 years," chanted protesters in demonstrations staged by the Common Forum opposition in four different parts of the capital Sanaa.

In reference to the ouster of Tunisian president Zine El Abidine Ben Ali, the demonstrators said he was "gone in just (over) 20 years."

But Yemeni Interior Minister Motahar Rashad al-Masri ruled out any resemblance between the protests in Yemen and the public outcry in the North African country that led to Ben Ali's departure.

"Yemen is not like Tunisia," he told AFP, adding that Yemen was a "democratic country" and that the demonstrations were peaceful.But the slogans chanted in Thursday's Sanaa demonstration which lasted for two hours were firm in demanding Saleh's departure.

"No to extending (presidential tenure). No to bequeathing (the presidency)," chanted demonstrators, insisting that it was "time for change."

"Common Forum go ahead. It is time for change," proclaimed banners carried in the protests.

Opposition Al-Islah (Reform) party MP Abdulmalik al-Qasuss echoed the demands of the protesters when he addressed them.

"We gather today to demand the departure of President Saleh and his corrupt government," he said.

A Common Forum activist said that the staging of the demonstration in four separate parts of the capital was aimed at distracting the security forces.

One area chosen for the protest was outside Sanaa University.Security measures at the demonstrations appeared relaxed, but were tight around the interior ministry and the central bank.

Saleh's ruling General People's Congress (GPC), meanwhile, organised four simultaneous counter demonstrations which were attended by thousands of the government's backers.

"No to toppling democracy and the constitution," the president's supporters said on their banners.

On Saturday, hundreds of Sanaa University students held counter protests on campus, with some calling for Saleh to step down and others for him to remain in office.

Saleh, who has been president for decades, was re-elected in September 2006 for a seven-year mandate.

A draft amendment of the constitution, under discussion in parliament despite opposition protests, could allow him -- if passed -- to remain in office for life.

Saleh had urged the opposition which rejected the amendment to take part in April 27 parliamentary elections to avoid "political suicide."

The mandate of the current parliament was extended by two years to April under a February 2009 agreement between the GPC and opposition parties to allow dialogue on political reform.

The reforms on the table included a shift from a presidential regime to a proportional representation parliamentary system and further decentralisation of government -- measures that have not been implemented.

The dialogue has stalled, and a special committee set up to oversee reform has met only once.

Saleh is also accused of wanting to pass the reins of power in the impoverished Arabian Peninsula state to his eldest son Ahmed, who heads the elite Presidential Guard.