The blast, 138 kilometres south-east of Sanaa, caused damage to the populated district of Al Najda in Thamar city.
“The explosion occurred at a military base in the residential area of Al Najda, causing a large blaze with a plume of dark smoke over the residential area,” he said.
Houthi militias have been using the police training centre in southern Thamar as a missile launch pad for years.
The explosion caused damage to many houses surrounding the base and caused civilian casualties.
“We heard the sirens of the ambulances rushing to the area, going back and forth to the public hospital in the city many times,” the source said.
A report by the investigative website Bellingcat in February concluded that the Houthis used the same military base to launch ballistic missiles aimed at Yemen’s power-sharing government as it arrived in Aden airport on December 30, last year, killing more than 35 people.
“Using the intersection method, it was possible to identify the vicinity from which these missiles were launched,” the website reported.
“This location is marked as a police training centre on Google Maps, which is consistent with multiple social media posts claiming that a missile launch occurred at a police base.”
The explosion at the site comes as fierce clashes between the Houthi rebels and tribes loyal to the Yemeni government continue in the province of Marib, the last government stronghold in the country's north.
Tribal sources told The National on Sunday that fighting has been raging in the Al Naja area, in Al Jubah district, southern Marib.
“We launched a large-scale offensive against the Houthi militias in the southern outskirts of Al Jubah,” said Sheikh Mohammed Al Qardaie, a tribal leader in southern Marib.
“We regained control over strategic posts during the attack” he said. Dozens of Houthi fighters were killed in the offensive, he added.
Hundreds of Houthi militias, visible in the treeless terrain around Marib, have been killed by Saudi-led coalition air strikes in recent weeks, local commanders and Saudi Arabia's air force said.
Fighting intensified in southern Marib while thousands of civilians were still reportedly trapped in the rugged, parched terrain of the oil-rich province.
But there is no sign of a ceasefire on the horizon and international aid agencies, including Unicef and the International Committee of the Red Cross, are warning of impending famine.
“The ICRC remains deeply concerned about the humanitarian situation in Marib. We continue to urge those involved in the hostilities to facilitate the evacuation of the sick and wounded, create conditions for humanitarian aid to reach those in need, and protect civilians from harm” Basheer Omar, the Yemen-ICRC spokesman, told The National.
According to Mr Omar, the ICRC succeeded in delivering emergency aid to medical centres in Marib on both sides of the front lines.
“Last Sunday, Marib Military Hospital was resupplied with surgical materials, and on the same day, we sent a lorry with medical supplies to Al Abdiyah,” Mr Omar said.