A military showdown is looming in Yemen after the defence minister announced that the army would defend the president against any "coup against democracy". His statement came hours after 12 military commanders, including a senior general, defected from the regime and promised to protect anti-government protesters in the capital, Sana'a.
"The armed forces will stay faithful to the oath they gave before God, the nation and political leadership under the brother president, Ali Abdullah Saleh," said Mohammed Nasser Ahmed, the defence minister. "We will not allow under any circumstances an attempt at a coup against democracy and constitutional legitimacy, or violation of the security of the nation and citizens."
Explosions and shooting heard briefly on Monday evening near a presidential compound in the eastern port of Mukalla added to the sense of tension, as did a raid on al-Jazeera's offices in Sana'a by gunmen who seized broadcasting equipment.
Yemen's president, Ali Abdullah Saleh, suffered a significant blow when General Ali Mohsen al-Ahmar, his longtime confidant and head of the Yemeni army in the north-west, announced that he would support "the peaceful revolution" by sending soldiers under his command to protect the thousands gathered in the capital to demand that Saleh step down.
"According to what I'm feeling, and according to the feelings of my partner commanders and soldiers … I announce our support and our peaceful backing to the youth revolution," Ali Mohsen said.
Minutes after his defection, tanks belonging to the republican guards, an elite force led by Ahmed Ali, the president's son, rolled into the streets of Sana'a, setting the stage for a confrontation between defectors and loyalists.
Republican guard tanks took up strategic positions across the city, at Saleh's residence, the ministry of defence and at the central bank. Tanks of Ali Mohsen's 1st armoured division took up positions elsewhere in the city. Ali Mohsen's pledge opened the floodgates to a stream of other defections. Scores of ambassadors, regional governors, editors of government newspapers, prominent businessmen and senior members of the ruling party either quit or announced their allegiance to the protesters.
Within hours, seven Yemeni ambassadors – to Japan, Syria, the Czech Republic, Jordan, China, Saudi Arabia and Kuwait – announced they were standing down.
"The regime is crumbling. There is very little support left for the president now," said Mohammed al-Naqeeb, head of the ruling party in Aden, who also resigned.
At first, protesters gathered at Sana'a University were unsure what to make of the general's pledge: many feared an increased military presence might mean further attacks.
But confusion soon gave way to jubilation as hundreds of soldiers from the 1st armoured division arrived on foot, greeted by protesters, who kissed them and hoisted them on to their shoulders.
The soldiers mingled with protesters as Ali Mohsen's men picked their way through the tent-filled streets, cheered on by young men waving placards carrying pictures of the general.
Soon a line of policemen, soldiers and businessmen had formed, each waiting their turn to step up on to a huge stage and announce their resignations to a roaring crowd of thousands.
"We've bought you a birthday present, Ali – it's a plane ticket to Saudi," shouted Haeman Saeed, a leading Yemeni businessman, after announcing his resignation from the ruling party.
"The army are with you," roared Abdallah al-Qahdi, a senior military general from Aden who was fired from his position last week for refusing to quell a peaceful demonstration.
Qahdi said many regime insiders had been waiting for someone like Ali Mohsen to lead the way. He expected most of the army to have defected by nightfall.
But for the time being, the outcome remained unclear. Analysts said there may soon be a violent clash within the military between those who have defected and the significant portions of the army still under the president's control.
Abdul Irayani, a Yemeni political analyst, said: "Unfortunately, the president and his sons still have control over powerful sections of the military, including the republican guard and the air force.
"We are all praying that Saleh leaves quickly and quietly to prevent the situation deteriorating rapidly."
Others suggest that the resignations may have been negotiated behind the scenes. "I believe this is a step towards a transitional military government in Yemen," said Abdullah al-Faqih, a professor at Sana'a University.
The army split followed Saleh's decision to sack his entire government after tens of thousands of mourners flooded the streets of the Yemeni capital on Sunday for a mass funeral for the 52 protesters killed in a sniper attack by loyalists on Friday.
The president asked the cabinet to serve as a caretaker government until he forms a new administration.
Piling further pressure on Saleh, the country's most powerful tribal confederation also called on him to step down.
Ali Mohsen is between 50 and 60 years old, and is generally perceived to be the second most powerful man in Yemen.
Most reports indicate he is the cousin of Saleh's two half-brothers, although there is much confusion on this matter, with some claims that he is himself a half-brother to Saleh.
Ali Mohsen al-Ahmar's name is mentioned in hushed tones among most Yemenis, and he rarely appears in public. Those who know him say he is charming and gregarious. But as commander of the north-east region and the 1st armoured division, Ali Mohsen acted as Saleh's iron fist.
The area he controls includes the governorates of Sa'ada, Hodeidah, Hajja, Amran, and Mahwit, and he is more powerful than any governor.
Ali Mohsen was instrumental in the north's victory in the 1994 civil war and in crushing the recent Sa'ada uprising. It is estimated that he controls more than half of all military resources and assets.