Yemen's army on Tuesday launched an offensive against tribesmen suspected of repeatedly sabotaging an oil pipeline in east Yemen, sparking clashes which left 17 people dead, tribal sources said.
The dead included 10 tribesmen and seven soldiers, said the sources, who added that the army offensive in Marib province's Habab valley, 140 kilometres (87 miles) east of the capital Sanaa, was launched in the early hours of the morning and was backed by air raids.
The sources said the army was "randomly shelling" the area where some al-Qaeda militants joined tribesmen ranks in battling Yemeni troops. Marib is a major al-Qaeda stronghold in the country.
Tribesmen, of whom 18 were also wounded according to the same sources, fought back with rocket-propelled grenades and machine guns, one source said.
The army did not immediately confirm the deaths of four soldiers.
According to official figures, lost production due to attacks on the oil pipeline in the east cost the government more than $1 billion dollars in 2012, while oil exports fell by 4.5%.
A tribal source told AFP that the offensive was aimed against prominent figure Salah bin Hussein al-Dammaj, who has allegedly blown up the pipeline several times to pressure the authorities to pay him 100 million riyals ($480,000) in compensation for land he claims was taken from him in Sanaa.
The 320-kilometre (200-mile) pipeline carries oil from Safer oilfields in Marib to an export terminal on the Red Sea. It produces around 180,000 barrels per day.
Attacks on oil and gas pipelines by Al-Qaeda militants or by tribesmen seeking to extract concessions from the central government are common in Yemen.
In July, Petroleum and Minerals Minister Hisham Abdullah said the impoverished Arabian Peninsula country had lost more than $4 billion (3.1 billion euros) in revenues since February 2011 due to the attacks.
Yemen produces about 300,000 barrels of oil a day, most of which is destined for export.
al-Qaeda, in the Arabian Peninsula (AQAP), took advantage of the weakness of Yemen's central government during an uprising last year against now ousted president Ali Abdullah Saleh, seizing large swathes of territory across the south.
But after a month-long offensive launched in May by Yemeni troops, most militants fled to the more lawless desert regions of the east.
Tribes in Yemen as well as AQAP militants often resort to violence and abducting foreigners to force the government to respond to their demands.
On Friday, two Finns and an Austrian were kidnapped in Sanaa, suspectedly by Al-Qaeda-linked gunmen.
State news agency Saba reported Tuesday that "security services are still carrying out vast search operations to hunt down the abductors and the place where the hostages are held to secure their safe release as soon as possible."