HONG KONG — A morning run can be the perfect way to overcome jet lag, but usually not when it’s through the choking haze of auto exhaust and industrial discharge.

In a Friday morning post, Facebook’s co-founder and chief executive, Mark Zuckerberg, announced his arrival in Beijing with a blithe message about what must have been a dizzying jog through the center of China’s capital, which has been suffering from a weeklong bout of hazardous air pollution.

“It’s great to be back in Beijing! I kicked off my visit with a run through Tiananmen Square, past the Forbidden City and over to the Temple of Heaven,” Mr. Zuckerberg wrote on Facebook, most likely using a virtual private network to get around the Chinese government Internet filters, which block his site.

In a photo accompanying the post, made about 10:30 a.m., Mr. Zuckerberg smiles alongside several running companions in front of the famous portrait of Mao Zedong that overlooks Tiananmen Square.