Fierce clashes between Yemeni government forces and al Qaeda-linked militants in southern Yemen overnight killed 14, including 12 militants, officials said on Wednesday.
Late on Wednesday, loud explosions and exchanges of fire were heard in the capital Sanaa in the neighbourhood where the chief of the main tribe opposing Yemen's president lives. There were no immediate reports of casualties.
Three explosions were also reported near police stations and an intelligence office in Aden in southern Yemen.
A military official said on Wednesday negotiations in the south with the fighters to end the bloodshed there were deadlocked.
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Islamic militants linked with al Qaeda have taken advantage of the turmoil gripping Yemen over anti-government protests, seizing control of a number of towns and the provincial capital of the southern province of Abyan.
The militants have controlled the towns for months, terrorising the locals. In recent weeks, the military has gone on the offensive, but fierce fighting has not shaken the militants' hold on the area and has left thousands of civilians displaced.
The fighting and the internal turmoil are closely related.
Ali Abdullah Saleh, Yemen's leader of nearly 33 years, has held onto power in the face of massive protests demanding his ouster since February. He insists that if he leaves, al Qaeda will take over the country.
The West views the al Qaeda branch in Yemen as the most active and dangerous, and has been linked to several nearly successful attacks on US targets, including the plot to bomb a Detroit-bound airliner in December 2009.
The group also put sophisticated bombs into US-addressed parcels that made it onto cargo flights last year.
Some opposition figures have suggested Saleh's forces have allowed the militants to make gains to underline his warning of the consequences if Saleh departs.
Saleh, who is still recuperating in Saudi Arabia after a June attack on his compound in Yemen's capital, Sanaa, said the United States and Saudi Arabia have supported his efforts to retake the towns.
In Abyan, two competing military units, one under Saleh's command and the other under the leadership of a defecting general, are fighting the militants in Abyan.
This has led to internal conflicts.
The unit led by the defecting leadership has made headway in reclaiming control over the provincial capital Zinjibar this week, seizing parts of it.
The government said the whole capital has been liberated but a few days later, the military came under attack from the militants, who were clearly still in the area.
In the latest fighting, witnesses said they heard a fierce exchange of gunfire and shelling in Zinjibar and in a town to the west.
The fighting lasted into the early hours of Wednesday.
A Yemeni undertaker said that he buried 12 militants and two civilians killed in clashes.
The undertaker spoke on condition of anonymity because of security concerns.
