Gunmen abducted the chief of staff to Yemen's president early Saturday in the center of the capital, Sanaa, security officials said, starkly highlighting the unrest plaguing the Arab world's poorest country.

The kidnapping of Ahmed Awad bin Mubarak comes as Yemen remains gripped by Shiite Houthi rebels and battered by regular al-Qaida attacks.

Officials said gunmen kidnapped bin Mubarak and his two guards when they stopped their car in central Sanaa. They said there was no ransom demand made.

One of the youngest politicians in Yemen, 46-year-old businessman-turned-political figure bin Mubarak emerged during the uprising that forced longtime leader Ali Abdullah Saleh to step down in a U.S.-backed agreement.

The officials, who spoke on the condition of anonymity because they were not authorized to brief journalists, said they suspect his kidnappers are Shiite Houthi rebels. The Houthis seized large areas of Yemen, including Sanaa, last year as part of their protracted power struggle with President Abed Rabbo Mansour Hadi.

Critics say the Houthis are a proxy for Shiite Iran, charges the rebels deny.

Bin Mubarak is personally at odds with the Houthis. He was the president's choice for prime minister last October, but his nomination was derailed after Houthis opposed him for his ties to the president.

Meanwhile Saturday, thousands demonstrated in central Sanaa against the Shiite rebels in a protest called by civil society groups. They marched to the Defense Ministry, chanting: "Revolution against the Houthis! Revolution against terrorism!"

A separate protest in front of the French Embassy saw demonstrators express their outrage over the satirical Paris newspaper Charlie Hebdo depicting the Prophet Muhammad.