|Tens of thousands of protesters marched to the capital's university, joined by opposition parties [A-SH]
Yemen's president has hit out at Israel and the US, accusing them of destabilising his country and the Arab world as protesters demanding his ouster press ahead with demonstrations.
Ali Abdullah Saleh's comments on Tuesday marked his harshest public criticism yet of the US, a key ally with which his government is battling al-Qaeda pockets in the Arabian pensinsula.
He said "there's an operations room in Tel Aviv with the aim of destabilising the Arab world" and that it is "run by the White House".
The United States said on Tuesday Saleh "knows better" than to charge that a foreign plot was behind unrest in his country, saying he should respond to his people's aspirations.
"The protests in Yemen are not the product of external conspiracies. President Saleh knows better. His people deserve a better response," PJ Crowley, the US state department spokesman, said in a message on Twitter.
An hour after Saleh's speech, tens of thousands of protesters marched to the capital's university, joined for the first time by opposition parties.
Sheikh Abdul-Majid al-Zindani, a cleric the US accuses of having links to al-Qaeda, was present at the gathering and declared his support for the protesters, calling for the establishment of an Islamic state.
Saleh, speaking to faculty at Sanaa University, accused the US president of meddling in the Middle East. "Mr Obama, you're the president of the United States; you're not the president of the Arab world," he said.
Al Jazeera's Hashem Ahelbarra, reporting from Sanaa, said: "He [Saleh] is asking the international community to stop interfering in the affairs of the Arab world ... It's a very significant development; it shows Saleh is not willing to bow to the demands of the protesters."
Protesters pressed ahead with demonstrations despite an offer a day earlier from the president to form a unity government. Saleh has been in power since 1978.
Huge crowds poured onto the streets of Sanaa in what the opposition hailed as the biggest protest yet against Saleh's three-decade rule.
Tuesday's protest is the latest in a series that have rocked the country for weeks and claimed at least 24 lives.
The protesters chanted one word: "Leave", in reference to Saleh who until Monday was reluctant to address their demands and said they could not achieve their goal through "anarchy and killing".
Meanwhile on Tuesday, Saleh sacked the governors of five provinces where anti-regime protests have been raging, mostly in the regions that constitute former South Yemen.
An official announcement said Saleh has removed the governors of Aden, Lahij and Abyan in the south, as well as Hadramaut in the southeast and Hudayda in the west.
"Saleh is clearly concerned about the mounting ant-government momentum in the southern provinces where the secessionist movement is strong, a hotbed of dissent, that saw many clashes recently," Ahelbarra said.
"The sacking shouldn't be seen as a sign of further defections but rather Saleh being frustrated with the deteriorating situation in the south where the secessionists have been able to gain ground and where demands for independence are gaining momentum.
"So he would like to tell the southerners that by sacking these people he cares about their grievances. Ironically the governor of Aden threatened to resign many times in the past over sweeping powers granted by Sanaa to Aden security chief," he said.
On Monday, Saleh appeared to back down, saying he would accept members of the opposition in a new government if the protesters stopped their demonstrations.
The offer was swiftly rejected by both opposition figures and protesters who described it as an outdated "tranquiliser".
"The president is saying that 'I cannot keep giving you concessions' because you'll ask for more," said our correspondent.
"The opposition is gathering to try to come up with a final statement later in the day. The demands of the opposition are high: They are saying that the only way to defuse tension in Yemen is to see Saleh quit power, but he is saying that the ballot box is the only [thing] decide."
One protester said the demonstration was named the "Day of Rage for the sake of the martyrs who have been killed in Aden," a reference to the main city in southern Yemen, which has seen some of the heaviest violence directed at protesters.
"The regime gangs and its followers suppressed them, so we will protest here and stand fast until the regime steps down," said Abdul Rahman Kabati.
Many protesters are angry at widespread corruption in a country where 40 per cent live on $2 a day or less and where university graduates without connections struggle to get jobs. Youth unemployment is rampant.
Yemen is also riven with regional strife, with Shia rebels in the north and separatists in the south demanding fairer political participation.
Separatist fighters, meanwhile, clashed with the army on Monday, killing one officer and wounding a second, as unrest sweeps across the country.
The fighting happened in the district of Habilayn, where secessionist sentiment runs high.
Nasser al-Khabji, a leader in the separatist Southern Movement, told the Reuters news agency that more militants were joining the clashes.
"More separatist supporters are moving into the area, the situation is tense," he said.
In a separate development, tribesmen kidnapped an Uzbek doctor working in the province of Shabwa, an area of central Yemen where both separatists and al-Qaeda fighters are active, late on Monday.
Abdulhamid Jun was taken to the neighbouring southern Abyan province, where an air strike against al-Qaeda suspects in December 2009 killed dozens of people in the town of al-Maajala.
"They took him to pressure the government to hold the people behind the air strike accountable," a tribesman in Shabwa told Reuters. "The people are upset with the government for not dealing with this issue."
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Source: Al Jazeera and agencies