Gulf Arab states have demanded the restoration of government authority in Yemen, issuing a thinly veiled criticism of rebels with ties to Iran who have taken control of the capital, Sanaa.
Fighters from the Shia Houthi movement seized Sanaa on September 21 after overrunning an army brigade affiliated to the Sunni Islah party, making them effectively the power brokers in the country.
The Houthis have since refused to quit the capital, which they control despite an agreement they signed with President Abd-Rabbu Mansour Hadi to make them a part of the government.
Houthis - Rebel group at war with the government since 2004. Signed a deal with the government last month for more political inclusion after mass protests and bloody clashes.
Al-Islah - Islamist party that draws support and membership from heavily armed Sunni tribesmen, and is instrumental in rallying support behind the army and the government. The Houthis have identified the party as its arch-enemy.
Al-Qaeda in the Arabian Peninsula - A merger of the Yemeni and Saudi branches of al-Qaeda. Seized large swathes of territory in the south and the southeast after the uprising in 2011. Launched many attacks on armed forces and central authority establishments.
The Southern Separatist Movement - Umbrella group that wants the south to break away from the north and reinstate the former Socialist state that existed until 1990.
Reuters reported that an emergency meeting of Gulf Cooperation Council (GCC) interior ministers expressed deep concern about what it termed threats to the Yemeni government and its institutions and the theft of the "properties and capabilities" of the Yemeni people.
GCC states would not "stand idly" in front of foreign intervention, the ministers said in a statement after the meeting late on Wednesday in the Saudi Arabian Red Sea port of Jeddah. It did not identify any foreign power.
"Yemeni and GCC security is indivisible," the statement said, demanding the return of official buildings to state control and the return of all looted weapons, military equipment and money.
The GCC comprises Saudi Arabia, the United Arab Emirates (UAE), Oman, Bahrain, Kuwait and Qatar.
In a statement, al-Qaeda's Yemen wing, al-Qaeda in the Arabian peninsula (AQAP)) called on fighters to attack Houthis.
AQAP is fighting to topple Hadi's rule, but has turned its attention to the Houthis since their capture of Sanaa, carrying out a number of deadly attacks.
"Do not leave a checkpoint for them that you do not strike, nor a headquarters that you do not bomb," said an AQAP statement posted online, according to the SITE monitoring service.
"Lie in wait for them, cause harm to them on the roads, tighten the ambushes for them, and do not let them feel safe."
Since September 21, armed Houthi tribesmen have been patrolling the streets, operating checkpoints and controlling access to several central government buildings.
Related: Yemen school defies Houthi occupation
The stability of Yemen is a priority for the United States and its Gulf Arab allies because of its position next to Saudi Arabia and shipping lanes which run through the Gulf of Aden.
Saudi Arabia views the Houthis, who hail from the Shia Zaidi sect, as allies of arch-rival Iran.
The Houthis acknowledge they are on good terms with Iran, but insist they are not backed by Iran. Tehran denies interfering in Yemen.