Somali President Sheikh Sharif Sheikh Ahmed came to power in January
Somali President Sheikh Sharif Sheikh Ahmed has declared a state of emergency in the country.
He told a news conference in Mogadishu it was because of "intensifying violence across the country".
The fragile UN-backed transitional government is coming under intense pressure from Islamist militias that control swathes of the country.
On Saturday, Somalia asked for urgent foreign military intervention - a call backed by the African Union.
"As of today, the country is under a state of emergency," President Ahmed told reporters in the capital, according to AFP news agency.
However it is not clear what difference this will make on the ground.
President Ahmed, a moderate Islamist, took office in January but even his introduction of Sharia law to the strongly Muslim country has not appeased the guerrillas.
Since 7 May, an alliance of militant Islamist hardliners, which controls much of southern Somalia and parts of the capital Mogadishu, has been locked in ferocious battles with pro-government forces.
Last week alone, the security minister, Mogadishu's police chief and an MP were killed.
On Saturday, parliamentary speaker Sheikh Aden Mohamed Nur asked for foreign intervention within 24 hours to help prop up the government.
He said the radical Islamist group al-Shabab, which is accused of links to al-Qaeda, was using foreign fighters.
But al-Shabab says the suicide bomber who killed Security Minister Omar Hashi Aden and at least 34 others in Beledweyne last Thursday was a Somali man and named him as Mohamed Deerow Sheikh Adam.
On Monday, AU Commission Chairman Jean Ping said in a statement the Somali government had "the right to seek support from AU member-states and the larger international community".
The African Union has some 4,300 peacekeepers in Mogadishu, but its mandate prevents them from attacking the Islamist hardliners except for in self-defence.
The BBC's Elizabeth Blunt in Addis Ababa says all eyes are on Ethiopia to see if it will respond to the plea for intervention.
Ethiopia's troops left Somalia in January under a UN peace deal after spending two years helping government forces against insurgents.
On Sunday, Ethiopian Information Minister Bereket Simon said: "Any further action from Ethiopia regarding Somalia will be done according to international community decision."
Our correspondent says it remains to be seen whether the AU's blessing is enough to tempt Ethiopia to return.
Kenya's Prime Minister Raila Odinga has ruled out sending out Kenyan troops to Somalia, which has been without an effective government since 1991.
Its transitional government controls only parts of Mogadishu, but little of the rest of the country.
Some four million people in Somalia - or about one-third of the population - need food aid, according to aid agencies.