An airstrike by the Saudi-led coalition targeted a building used by police in Yemen's capital, Sanaa, killing at least 26 people and wounding about 15, security officials said on Monday.

Security forces swiftly sealed off the area as earth-moving equipment arrived to help with the search for bodies and survivors under the debris.

The security officials, who are loyal to anti-government Shia rebels known as the Houthis, said some 30 people were believed still trapped under the debris of the badly damaged building in central Sanaa.

The officials had initially announced that 20 people were killed, but later said that six more bodies were unearthed from under the debris. The strike also destroyed police vehicles parked in the facility's courtyard while nearby homes suffered some damage, they said.

The dead and wounded were policemen and Houthi rebels, they said. The targeted building was partially used as a gathering point for security forces and on occasion used by the Houthis as an assembly point for forces headed to deployment elsewhere in Yemen.

The airstrike happened shortly before midnight on Sunday, according to the officials, who had no further details. Reporters were barred from approaching the facility. The officials spoke on condition of anonymity because they were not authorized to speak to the media.

The Saudi-led coalition began airstrikes against the Houthis and their allies in March 2015, siding with the internationally recognized government.

Meanwhile, the Integrated Regional Information Networks, a Nairobi-based humanitarian news agency, announced the death of one of its contributors in Yemen. In a statement, it said 35-year-old Almigdad Mohammed Ali Mojalli was killed Sunday just outside Sanaa in an "apparent" airstrike.

Mojalli also contributed from Yemen to Western media outlets, including Voice of America and Britain's Daily Telegraph newspaper, said the statement.

The fighting in Yemen has killed more than 5,800 people since last March when the Saudi-led coalition began the air campaign.

Also Monday, gunmen on a motorcycle shot and killed Abdel-Hadi Abdel-Qawi, a prominent judge in the strategic port city of Aden.

The shooting happened in the city's Mansoura neighbourhood, officials there said. No one immediately claimed responsibility but al-Qaeda has carried out similar attacks in the past.

Local affiliates of al-Qaeda and the Islamic State have exploited the chaos of Yemen's civil war to expand the territory under their control in southern and eastern Yemen. Militant attacks on officials have been on the rise in Aden ever since they gained a foothold there last year.