The Yemeni army launched a major assault on Sunday on tribesmen suspected of repeatedly blowing up the main oil export pipeline and attacking power lines, officials said.

The officials said some 30 tanks and other armoured vehicles were participating in the offensive against tribal fighters in the Wadi Obaida area of the central oil-producing province of Maarib.

"The army is shelling areas containing armed men who blew up the oil pipeline and power lines in Maarib, " a security source said, adding that some houses had been destroyed.

The fighters are said to be using infrastructure sabotage to press the government for handouts and the release of jailed tribesmen.

Yemen has been struggling to restore normality after President Abd-Rabbu Mansour Hadi was elected in February following a year of protests that forced his predecessor Ali Abdullah Saleh to step down after 33 years in power.

Restoring stability is a priority for the United States and its Gulf allies because of Yemen's strategic position next to top oil exporter Saudi Arabia and major shipping lanes, and because it is home to a major wing of al Qaeda.

But armed groups have repeatedly sabotaged government installations, especially oil and gas pipelines and power facilities.

The last attack came on Saturday, half an hour after engineers completed repairs to one of at least three ruptures in the pipeline which transports crude oil from Maarib to the Ras Isa export facility on the Red Sea.

On Sunday, gunmen opened fire on a power station in the Damashqa area of Maarib, putting the facility out of action.

Fighters have also repeatedly targeted Yemen's gas pipeline, which feeds the country's only liquefied natural gas (LNG) terminal, a main source of state revenue, forcing the government to deploy troops to protect it.

The demands of the tribesmen are said to include government handouts or the release of relatives jailed for common crimes, attacking security forces or associating with al Qaeda.

"Those who carry out these attacks are individuals, but they seek refuge and protection from their tribes," a Yemeni cabinet minister told Reuters.

"They are often demanding financial compensation or the release of relatives jailed for criminal offences."

Yemeni officials say that under Saleh, the Yemeni government paid tribesmen monthly protection money to refrain from attacking power lines and the oil pipeline.

Hadi made some payments after he came to power but then stopped.

Yemen has been struggling to finance its daily needs. Donors have pledged a total of $8 billion to help the poorest Arab country overcome financial challenges. But little has trickled into Yemen so far.

Some 40 percent of the population lives below the poverty line of $2 per day. Yemen relies on revenues from e nergy sales for 60 percent of its income.