Just hours after Shiite Houthi rebels were reported to have overrun a provincial town in southwest Yemen, suspected Al-Qaeda militants were reported to have seized control of another town nearby, a security official said Thursday.
Five policemen were killed in the overnight offensive by militants on the town of Udain, 20 kilometres (12.5 miles) west of the now rebel-controlled Ibb, the security official and local sources said.
The gunmen attacked the police headquarters, which was set ablaze, and the offices of the local government, as well as the post office.
Al-Qaeda is active in several Yemeni provinces, mainly in the south and southeast, where repeated government military campaigns drove the network's militants out of key cities they once controlled.
The attack on Udain appeared to be in retaliation for the Shiite Houthi rebels' control of Ibb, a local official said.
Already in control of Sanaa and the strategic port city of Hudeida, the rebels on Wednesday appeared to have taken control of the Dhamar and Ibb provinces, security officials said.
Just as in Sanaa and Hudeida, the rebels faced no opposition as they entered the two provinces and set up checkpoints, the officials said.
The rebels have been taking advantage of a power vacuum in Yemen to seize control of significant areas, threatening the authority of the Sunni-led central government.
But their expansion threatens of an open confrontation with Al-Qaeda.
Deadly fighting broke out Tuesday when the Houthis tried to expand out of the town of Rada in central Baida and clashed with Al-Qaeda militants.
Five rebels, six suspected Al-Qaeda militants and a civilian were killed during the fighting in Rada, a security official and tribal sources said Wednesday.
An Al-Qaeda-linked group on Thursday claimed responsibility for the killing of an army officer in Yemeni capital Sanaa one day earlier.
The self-styled Ansar al-Sharia group said on Twitter that its fighters had shot dead the officer in eastern Sanaa.
The group claimed that the slain officer was a "senior leader in the Shiite Houthi group".
There has been no comment from Yemeni authorities on the statement.
In a further act of violence, late Wednesday armed tribesmen blew up an oil pipeline in Yemen's eastern Ma'rib province, a local official has said.
The tribesmen detonated the pipeline in the Anshar district in the province, the official told Anadolu Agency.
There has been no claim of responsibility.
Impoverished Yemen, a key ally in US efforts to combat Al-Qaeda, has been wracked by political turmoil and sporadic violence since an uprising toppled strongman Ali Abdullah Saleh in 2012.