About 20 soldiers were killed and scores of others injured when suspected al-Qaida militants carried out attacks on government institutions in the southern province of Lahj on Friday evening, a military official told Xinhua.
"Gunmen suspected of belonging to the al-Qaida group launched attacks at the same time on the government compound and the intelligence offices in Houta city, Lahj's provincial capital, killing about 20 soldiers and destroying a number of buildings," the local military source said on condition of anonymity.
They also wounded dozens of soldiers and kidnapped some officers, the source said.
The attackers established several checkpoints around the city's main entrances and attempted to take full control over the town, the source added.
Security deteriorated in Yemen as the Shiite Houthi group stepped up confrontations against tribal militia and army that support President Abd-Rabbu Mansour Hadi who fled house arrest by the Houthi last month and resumed duties in the southern port city of Aden.
Earlier in the day, the Islamic State (IS) claimed responsibility in an online statement for three bombing attacks in Yemen's capital Sanaa and Saada province that killed 137 people during Friday prayers.
Meanwhile, the Yemen-based al-Qaida in Arabian Peninsula (AQAP) has formally condemned the bombings at Houthi mosques.
According to an official statement from AQAP, the group denied any involvement or responsibility for today's bomb attacks on the Houthi mosques.
Yemen, an impoverished Arab country, has been gripped by one of the most active regional al-Qaida insurgencies in the Middle East.
Al-Qaeda in the Arabian Peninsula (AQAP), which emerged in January 2009 and also known locally as Ansar al-Sharia, had claimed responsibility for a number of attacks on Yemen's army and government institutions.