The American, British and European Union ambassadors to Yemen are trapped in an embassy surrounded by gunmen angry about efforts by Arab mediators to ease President Ali Abdullah Saleh out of power, the American envoy told CNN.
U.S. Ambassador Gerald Feierstein said the ambassadors of Saudi Arabia, Kuwait, Oman and the United Arab Emirates are also being prevented from leaving the UAE embassy.
Feierstein has contacted his superiors to say he is fine, a State Department official told CNN. The United Kingdom, European Union and Arab nations did not immediately confirm that their envoys were trapped.
The U.S. official believes the Yemeni government is behind the demonstration in Sanaa, the source said, declining to be named speaking about a sensitive ongoing situation.
Security forces were seen near the embassy but did not try to disperse the protesters, several dozen of who had machine guns,eyewitnesses said. Many more had pistols or batons, they said.
"We are not here to cause damage or hurt anyone, (but) we do not want the Gulf Cooperation Council to get involved in the Yemeni crisis," said Ali Aref, an armed tribesman at the UAE embassy.
The armed protesters accused the regional body of trying to force Saleh from power and chanted anti-GCC slogans, sources in Sanaa said.
Bahrain's Foreign Minister Khaled al-Khalifa said he was in touch with GCC Secretary-General Abdul Latif Zayani about the situation, calling it "volatile."
Saleh was originally expected to sign a deal Sunday brokered by Zayani, who is also at the UAE embassy.
But the Yemeni president raised a new obstacle earlier Sunday, refusing to recognize the opposition signature on it from the day before.
"President Saleh invited the JMP (opposition alliance) to sign the ... proposal at the presidential palace at 3 p.m. today. We hope the JMP accepts President Saleh's invitation," said Tareq Shami, a spokesman for Yemen's ruling party, the General People's Congress (GPC).
He insisted that the demand is not a complication, but rather common sense.
"Any agreement should never take place in closed-door meetings. This is commonly known and Saleh does not want to start the transition period in such a way," Shami said.
Thousands of Saleh supporters blocked roads leading to a building where Saleh was meeting with senior offcials from the ruling party Sunday, saying they would not let the president leave the compound and sign the proposal.
"We will not allow him to sign and step down in thirty days. The GCC proposal is against the will of the Yemeni people," said Sabri Ali, a Saleh supporter. "We will stand with Saleh against the criminals in the JMP and will not accept anyone to rule us expect Saleh."
Tribal leaders, meanwhile, put armed gunmen on main roads in anticipation of violence.
"Yemen is lawless today and our tribes are here to ensure that safety prevails in all circumstances," said Shaef Ali Arhabi, a tribal leader from Arhab region.
He supports the opposition, but pro-Saleh tribesman are on the streets as well.
Opposition officials rejected Saleh's proposal that they sign the agreement again on Sunday after putting their names on it Saturday.
"This is Saleh. His words are never trusted. No agreement is respected by him," said Mohammed Qahtan, a spokesman for the JMP.
An opposition youth leader accused Saleh of trying to weaken the JMP by making it "chase him from place to place" and predicted he would not sign in the end.
"The youth will not care if any signing takes place. Our demands are clear and Saleh will stand trial for all his crimes," activist Tawakkol Karman said.
Yemen, a key al Qaeda battleground and U.S. ally, has been roiled by protests for most of the year amid the background of anti-government demonstrations across much of the Arab world.
Saleh has ruled the country for 33 years.
Yemen's opposition signed the regionally brokered deal to result in his departure and end the country's grinding political crisis, opposition officials told CNN Saturday.
Previous attempts to reach a similar pact -- guided by GCC -- have come close to being finished, only to fall through.
Saleh is unpopular in many quarters of the country, but he has been a stalwart U.S. ally against terrorism.
U.S. Secretary of State Hillary Clinton said Saturday Yemen is in "trying times," with suppression and deaths of civilians.
"President Saleh needs to follow through on his commitment to transfer power. The government of Yemen must address the legitimate will of the people," she said in a statement.
Shami, the ruling party spokesman, said earlier that Saleh asked to delay the signing until Sunday because it's a national holiday.
"President Saleh will sign the GCC proposal and he asked.... days ago to delay the signing of the proposal until Sunday May 22, as this day is Yemen's unity holiday," Shami said.