The deployment, which was also reported by the Qatar-based and funded Al-Jazeera news network, marks a major escalation by the Saudi-led coalition that has been bombing the rebels from the air since March, and which includes Qatar.
The conflict pits the rebels, known as Houthis, against an array of forces, including supporters of Saudi-backed President Abed Rabbo Mansour Hadi, southern separatists, Islamic militants, and local and tribal militias.
Over 2,100 civilians have been killed in the fighting, according to the United Nations.
The Qatari troops have arrived in the central province of Marib, where a rebel missile strike killed 60 coalition forces on Friday, said the officials, who are loyal to Hadi.
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The officials spoke on condition of anonymity because they are not authorised to brief reporters.
If the pro-government forces defeat the rebels in Marib, it could pave the way for them to rapidly move into the Houthis' northern stronghold of Saada. The Houthis control the Yemeni capital, Sanaa, just to the west of Marib.
Former President Saleh is believed to have close ties to tribal leaders in Marib who are fighting alongside Hadi's forces.