Yemeni Shi'ite fighters shot dead three pro-government tribesmen, the Interior Ministry said on Wednesday.
Yemen's central government agreed a truce in February to halt the northern war, which has raged on and off since 2004.
In the country's south, where the government is trying to curb a secessionist movement, more than 20 armed men surrounded local security headquarters on Wednesday demanding the release of several separatists from prison.
Local officials said security forces were sending reinforcements to the besieged base and were also negotiating with the group.
Wednesday's Interior Ministry statement said the Shi'ite fighters had opened fire on members of the Ben Aziz tribe, killing three tribesmen and wounding three others including a passerby.
The Shi'ite fighters, who complain of discrimination by the government, said they attacked the tribesmen in response to an earlier assault on the same day when the tribesmen opened fire on a market and wounded three people.
They also accused the tribe of cutting off the main road connecting rebel stronghold Saada to the capital Sanaa.
ReutersLast Mod: 28 Nisan 2010, 21:53