Yemeni tribesmen opposed to President Ali Abdullah Saleh said they stormed a military base north of the capital and seized arms on Monday, while officials said the army killed 20 militants in the restive south.
Hameed Asim, a leader of tribesmen who have skirmished with troops from the elite Republican Guard led by Saleh's son, said tribal fighters killed several troops in the raid before withdrawing. Asim said seven tribesmen were killed.
The attack was the latest in a series of running battles between tribesmen in the Arhab region and forces backing Saleh, who is clinging to power despite 10 months of protest demanding he go and a slide towards civil war on the borders of oil giant Saudi Arabia.
In the south, the army killed 11 Islamist militants with artillery attacks against their positions near Zinjibar, the capital of Abyan province, a tribal official told Reuters.
Militants with suspected links to al Qaeda have seized swathes of territory in Abyan, taking advantage of turmoil in the Arabian Peninsula country.
The political standoff in Yemen has also re-ignited conflicts with separatists, and the rising violence has alarmed Riyadh and Washington, which funded Saleh as part of its campaign against al Qaeda.
Elsewhere in Abyan, security forces killed three suspected al Qaeda militants while searching for those behind a bombing that killed two passersby on Monday, a Defence Ministry website reported.
The bomb had been planted on a street in the town of Mudiyah apparently in retaliation for an attack in which security forces killed six militants and captured a local al Qaeda leader earlier on Monday, the website said.
Yemen's opposition has said it has finalised a deal with Saleh under which he is to transfer his powers to his deputy.
Saleh has three times backed down from signing an initiative presented by the six-member Gulf Cooperation Council (GCC) calling for the president to hand over his powers to his deputy, Abd-Rabbu Mansour Hadi, ahead of an early presidential election.
The crisis over Saleh's fate has brought economic paralysis and periodically halted oil production in one the world's poorest countries, which depends on crude exports for revenue to fund imports of staple foodstuffs.
(Reporting by Mohammed Ghobari in Sanaa and Mohammed Mukhashaf in Aden; Writing by Joseph Logan and Firouz Sedarat; Editing by Janet Lawrence)