Yemeni's leader has rejected demands to resign immediately, declaring that protesters must end his rule through elections rather than demonstrations - though he has not offered to call any.
But the protests are continuing, alongside external pressure, for President Ali Abdullah Saleh - who has said he intends to cling on to power until 2013 - to go.
Meanwhile, human rights groups have urged the Yemeni authorities to stop using excessive force to control anti-government demonstrations.
Twelve people have died so far, with many more injured and wounded.
At least six Yemeni protesters taking part in what appears to have been a peaceful sit-in were reportedly seriously injured in the city of Ta’izz on 18 February, when security forces attacked them with what eyewitnesses described as a hand grenade, with dozens more also injured.
Activists in the capital Sana’a told Amnesty International that they had been surrounded by security forces, aided by men described as “thugs”, who were firing at them and issuing beatings.
“The Yemeni authorities seem to be stepping up their crackdown on protesters and we are gravely concerned that if that continues, the death toll will inevitably rise,” said Philip Luther, Amnesty International’s Middle East and North Africa Deputy Director.
“Yemen’s government must allow people to peacefully assemble and protest,” he added.
Eyewitnesses in Ta’izz told the NGO that plain-clothes men believed to be members of the security forces, or individuals colluding with them, opened fire from civilian cars on protesters who had been staging a week-long sit-in in the city’s central Safir Square.
Security forces stationed close to the square reportedly did nothing to protect the protesters.
Eyewitnesses in Sana’a said to Amnesty that they had been surrounded and attacked by security forces and “thugs”.
“We are trying to hide but the security forces are pointing out our locations to the thugs. We are very scared, particularly because there are children with us. We’ve tried to get the children out of the area but the security forces have not allowed us to do so,” one activist told the respected human rights group.
In 17 February, protesters and journalists were reportedly attacked at demonstrations around the country, leaving at least 10 people injured.