One policeman was killed and three were wounded following clashes at a demonstration in the city of Aden on Monday, police said, dpa reported.
Brigadier General Abduallah Qairan, head of police forces in Aden, told the German Press Agency dpa by telephone that demonstrators at a sit-in at the banned al-Ayyam newspaper first opened fire on the police, who retaliated.
"Armed supporters of the newspaper opened fire on the policemen, killing one instantly and wounding three others, including a senior officer," Qairan told dpa, adding that the protest was unauthorized.
However, al-Ayyam editor Hisham Bashraheel said it was police who fired teargas and live ammunition at the newspaper building first.
The Security Commission in Aden said in a statement that legal procedures were underway to prosecute Bashraheel over the policeman's death.
Earlier Monday, anti-terrorism police raided a village near the Yemeni capital Sana'a and killed two al-Qaeda suspects as further embassies closed down for security reasons.
A government official told dpa that a third suspect was injured and arrested in the operation in Arhab district, around 30 kilometres north-east of Sana'a.
The official said the three were among a group of al-Qaeda militants believed to have been behind threats sent to the US and British embassies in Sana'a this week.
Tribal sources in Arhab said the main suspect managed to flee during the raid near the Bawsan village of Arhab district. "They wanted to capture Muhammad Muhammed al-Haneq, but (he) managed to escape," a source told dpa.
The US and British embassies in Sana'a extended their closure for the second day Monday over terrorist threats. The embassies in the Yemeni capital were first closed Sunday amid terrorism threats from the regional branch of al-Qaeda, a Yemeni security source said earlier.