Huge crowds poured onto the streets of the Yemeni capital Sanaa on Tuesday in what the opposition hailed as the biggest protest yet against President Ali Abdullah Saleh's three-decade rule.
The veteran leader, whose supporters staged a large counter-demonstration, dismissed the opposition rally as a copycat action mimicking protests in other Arab countries that he charged had been fanned by Israel and the United States.
He then sacked the governors of five provinces where anti-regime protests have been raging, mostly in the regions that made former South Yemen.
An official announcement said Saleh has removed the governors of Aden, Lahij and Abyan in the south, as well as Hadramut in the southeast and Hudayda in the west.
Saleh's opponents massed from early morning in streets leading to a square near Sanaa University, where students and pro-democracy demonstrators have been camped for more than a week.
"The people want Ali Abdullah Saleh to leave," the protesters chanted. "The people want to overthrow the regime."
Many of the protesters marched in white shrouds reading: "Either we live happily or we die as martyrs."
The opposition said half a million people turned out, although an AFP correspondent said that number was an overestimate.
"Since the sit-in began near Sanaa university, we have not witnessed such a turnout," one of the organisers, Hashem al-Sufy, said.
The ruling General's People Congress gave an even wilder exaggeration of the number of people at the counter-demonstration in Tahrir Square, putting it at 1.5 million. An AFP correspondent said the reality was a fraction of that.
Several opposition figures addressed the anti-government rally, including leading cleric Abdul Majeed al-Zendani, who is identified as a "global terrorist" by Washington.
Zendani said that the protest movement sweeping the Arab world was "a new, effective, fast, and non-destructive means of changing regimes."
Saleh hit back, in an address at Sanaa University. "The events from Tunisia to Oman are a storm orchestrated from Tel Aviv and and under Washington's supervision," he said.
"What is taking place on Yemen's streets is just a copycat attempt," he said. The protesters are "led from outside" and are in the pay of "Zionists," he charged.
Saleh lashed out at US President Barack Obama for his repeated calls for restraint by Arab regimes that had long been key allies and his support for the popular protests that ousted veteran leaders in Egypt and Tunisia.
"Every day we hear a statement by Obama... (saying) Egypt don't do this, Tunisia don't do that... What does Obama have to do with Oman, what does he have to do with Egypt? You are the US president," he said.
The Yemeni leader, in power since 1978, has repeatedly rejected calls for his resignation, insisting he will defend his regime "with every drop of blood."
His one concession has been to pledge not to seek re-election in 2013, something the opposition has dismissed as inadequate.
Thousands of protesters also turned out on Tuesday in the southern province of Lahij. In the town of Seiyun, in Hadramut province further east, security forces shot and injured two protesters, witnesses and medics told AFP.
In the main southern city of Aden, thousands took to the streets of Al-Mansura neighbourhood carrying black flags in mourning of protesters killed during violent clashes with the police, witnesses said.
Demonstrations were also reported in Maalla and Crater districts.
The UN human rights chief warned Yemeni authorities against violent repression of peaceful protests, saying that people have the right to express their grievances.
"People have the legitimate right to express their grievances and demands to their government," Navi Pillay, UN High Commissioner for Human Rights, said in a statement issued in Geneva.
"We have seen over and over again in the past few weeks that violent responses, in breach of international law, do not make the protesters go away and only serve to exacerbate their frustration and anger," she added.
At least 19 people, most of them in Aden, have been killed during protests and clashes across Yemen since February 16, according to an AFP tally based on reports by medics and witnesses
Rights group Amnesty International has put the toll at 27.