Battles raged on Monday in Yemen's southern city of Zinjibar as the army intensified its drive to crush Al-Qaeda militants, with tribal sources reporting 37 jihadists killed in two days of fighting.
A government official said meanwhile that suspected Al-Qaeda fighters blew up a gas pipeline in southeast Yemen late on Sunday, in retaliation for the latest attacks on their positions.
"We can hear from Aden the sound of shelling in Zinjibar," said a resident in Yemen's main southern city, which is about a 30 minute drive from Abyan's restive provincial capital.
AFP could not directly reach sources in Zinjibar as telephone lines there were cut, but a tribal source coming from the city said that 21 jihadists had been killed since Sunday.
Another tribal source said 10 militants were killed in a Monday air raid on Al-Qaeda hideouts in the coastal Shaqra area.
Six others died in another raid on their positions in the outskirts of Loder, also in Abyan, a source from the Popular Resistance Committees battling Al-Qaeda militants alongside the army said.
AFP could not independently verify the tolls.
Yemeni forces on Saturday launched a multi-pronged assault aimed at recapturing Zinjibar, held by the jihadists for a year.
The battles against the militants were being carried out with "US logistical support," a Yemeni military official told AFP on Sunday, a day after US drones killed 16 suspected militants in two separate attacks east of the capital Sanaa, according to an updated toll posted by the news website of the defence ministry, 26Sep.net.
The death toll includes two Saudis and an Egyptian.
According to the Yemeni official, speaking on condition of anonymity, 12 soldiers have also been killed since the all-out operation against Al-Qaeda was launched around Zinjibar.
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Meanwhile, suspected Al-Qaeda militants responded to the assaults by blowing up a gas pipeline supplying Yemen's Balhaf export terminal in the Gulf of Aden, a government official said on Monday.
"A gas pipeline was blown up near Mayfaa" in Shabwa province in southeast Yemen late on Sunday, the official there said.
"Al-Qaeda blew up the pipeline in response to the raids that targeted it" over the past week.
The attack took place around 20 kilometres (12.4 miles) from the Al-Qaeda stronghold of Azzan in Shabwa.
Witnesses told AFP flames were seen flaring into the sky from the site of the explosion that took place around midnight, some 30 minutes after soldiers guarding the pipeline clashed with a group of gunmen.
The amount of damage to the pipeline was not immediately clear and it was not known to what extent supplies of gas, from a field in Marib province, were affected.
Attacks on Al-Qaeda by Yemeni forces with US backing have intensified in recent weeks.
Early last week, air strikes by US drones in eastern Yemen killed jihadist network leader Fahd al-Quso, wanted by Washington in connection with the 2000 bombing of the USS Cole in Aden harbour.
Quso's name figured on an FBI list of most wanted terrorists, along with a reward of up to $5 million for information leading to his arrest.
John Brennan, US President Barack Obama's top counter-terrorism aide held talks in Sanaa on Sunday with Yemeni President Abdrabuh Mansur Hadi.
Their discussions revolved around "combatting terrorism" and attempts by Yemen's army to crush the local branch of Al-Qaeda, state news agency Saba reported.
Al-Qaeda's branch in Yemen has exploited the decline in central government control that accompanied Arab Spring-inspired protests that eventually forced president Ali Abdullah Saleh to cede power in February.