Shia Houthi rebels in Yemen are reported to have tightened their grip on the capital, Sanaa.
Witnesses said rebels were stationed outside the private home of President Abdrabbuh Mansour Hadi, replacing soldiers from the Presidential Guard.
On Tuesday, the Houthis shelled the house and seized control of the presidential palace complex.
Their leader, Abdul Malik al-Houthi, accused the president and other leaders of ignoring the people's interests.
He said the country had reached a critical and defining moment.
The main security body in the southern port city of Aden said the measure was necessary because of "dangerous developments in the capital", and because of the threat to the president, whom it described as "the symbol of national sovereignty and constitutional legitimacy".
The Houthis are also reported to have seized the country's largest missile base on a hilltop above Sanaa, in addition to taking control of most media outlets and besieging the house of Prime Minister Khalid Bahah.
The rebels say that the president remains in his private residence and is free to leave - although Abdul Malik al-Houthi has repeated his demand for Mr Hadi to implement a power-sharing deal.
There has been no public statement from Mr Hadi, who has received strong support from the UN Security Council.