Some 17 Yemeni policemen were wounded in an ambush by Shiite Huthi rebels as fighting between government forces and the rebels neared the capital, officials said on Sunday.
The Huthis -- also known as Ansarullah -- have been pushing out of their northern mountain strongholds towards Sanaa in a suspected bid to expand their sphere of influence as Yemen is reorganised into six regions.
"Armed militants belonging to the Ansarullah Huthi (rebels) opened fire at security patrols carrying out their duties in the capital" on Saturday, state news agency Saba said.
Militants blocked a road in Sanaa's Al-Jarraf district, where the rebels have a representative office near to the interior ministry, and opened fire on police patrols from surrounding buildings.
Seventeen policemen, including three officers, were wounded in the assault, it added.
Security officials told AFP the incident took place after authorities arrested two wanted rebels and tried to arrest others.
Ansarullah said in a statement security forces "targeted" the rebels' bureau in Sanaa to "ignite a meaningless war."
On Saturday, hundreds of Yemenis protested outside the presidential residence in Sanaa over what they say is the authorities' inaction over the Shiite rebel advance on the capital.
Battles between troops and rebels neared Sanaa on Friday, with clashes reaching the town of Bani Matar, only 15 kilometres (nine miles) northwest of the capital, tribal and security sources said.
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The sources said that "dozens" have been killed, but were unable to provide a toll.
Military officials have said Yemeni jet fighters have pounded rebel positions over the past two days, destroying an arms depot in the northern town of Hamdan, while army reinforcements have been deployed around Sanaa.
A new round of clashes between rebels and security forces erupted in Yemen's north a week ago, ending an 11-day truce agreed after mediation backed by United Nations envoy Jamal Benomar.
Huthis have been battling the central government for years from their Saada heartland, complaining of marginalisation under Saleh, who stepped down in 2012 after a year-long uprising.
They had said that a federalisation plan agreed in February following national talks as part of a political transition would divide Yemen into rich and poor regions.
They seized areas of Amran province in fighting with tribes in February that killed more than 150 people.
In addition to the Shiite rebellion, the government in Sanaa is also facing a southern separatist movement and an Al-Qaeda insurgency.
Members of the security forces, particularly officers, are frequently targeted in attacks.
"Unknown gunmen" shot dead General Abdullah al-Mehdar, an instructor at Yemen's military academy, as he was leaving a mosque in Sanaa late on Saturday, a security official told AFP.
The two assailants escaped in the vehicle they were travelling in, the same source said.
Al-Qaeda militants are usually blamed for such hit-and-run attacks. But members of the network have never claimed the assaults.