At least seven people have been killed, including three police officers, in the Somali capital, following the formation of a new anti-government alliance.
Violence has flared in Mogadishu over the past month
Armed insurgents staged a hit-and-run attack on a government base in north-east Mogadishu, leaving six dead, a police spokesman said.
Elsewhere, a police captain was shot dead by three men with pistols.
The new alliance has named former Islamist leader Sheikh Sharif Sheikh Ahmed as its chairman.
Prime Minister Mohamed Ghedi has criticised the new Eritrea-based grouping as "trouble-makers and terrorists".
"The government does not recognise the results of the so-called Asmara conference hosted by the Eritrean president, who is known to be the trouble-maker in the Horn of Africa," he said, according to the AP news agency.
The overnight Mogadishu attack was in Huriwa, seen as an insurgent stronghold.
"It was one of the heaviest attacks we have witnessed for months - they attacked us with a large number of fighters," said Abdi Hashi Aden, a police officer in the attacked camp.
Local resident Sahra Shiekh Muse said she witnessed a number of government soldiers forced to run out of the camp.
It is not clear whether Sheik Aweys will be an official in the alliance
Police spokesman Colonel Abdi Wahid Mohamed denied the claim.
The attacks came hours after a night-time curfew was relaxed for the Muslim holy month of Ramadan.
The new Alliance for the Liberation of Somalia (ALS) groups together former Islamists and opposition figures.
It aims to remove the Ethiopian-backed government by negotiation - or war.
"We have two-track options - first is the liberation of Somalia through military struggle, the second is through diplomatic efforts," said Zakariya Mahamud Abdi, spokesman for the Somali Congress.
The spokesman had a stark warning for Ethiopian troops, heavily deployed in Somalia since they rescued embattled transitional government forces last year.
"We warn Ethiopia to withdraw immediately. It is now or never and in a few weeks they will not have a route to withdraw," Abdi said.
Mr Ahmed has been named as ALS chairman and the head of its executive committee, Mr Abdi said.
After the Islamists were ousted from Mogadishu last December, western diplomats urged the government to seek reconciliation with those seen as moderates, such as Mr Ahmed.
Former speaker of parliament Sherif Hassan Sheikh Adan has been named as chairman of the central committee, seen as the equivalent of a parliament.
Islamists hold 45% of seats in the committee, compared to 25% to MPs like Mr Adan, who have fallen out with the government.
Other seats are held by members of the diaspora and civil society.
Sheikh Hassan Dahir Aweys, an architect of the Mogadishu insurgency and on the US list of terror suspects, says he does not hold a position in the alliance.
His presence at the talks led the US to threaten to include Eritrea as a state sponsor of terrorism.
Since their defeat by Ethiopia's vastly superior military force in December last year, the Islamists have resorted to guerrilla tactics, launching daily hit-and-run attacks on targets, mainly in Mogadishu.
The UN refugee agency says some 400,000 people have fled the fighting in the capital in the past four months as a result of the surge in violence.
The Islamists, along with other opposition leaders like Hussain Aideed, boycotted a reconciliation meeting sponsored by the transitional government last month.
Instead they chose to organise a meeting hosted by Ethiopia's arch-enemy, Eritrea.
Ethiopian Prime Minister Meles Zenawi has said his troops will withdraw once an African Union peacekeeping force arrives in Mogadishu.
But pledges by AU nations to contribute troops to the planned 7,000-strong peacekeeping mission have yet to be honoured and so far only 1,600 Ugandan soldiers have been deployed.