Reuters news agency quotes a police source as saying that it is not known how many people are involved in the abduction.
The state-run television channel Al-Iraqiya says 60 or more passengers were killed by the hijackers. The report could not be independently confirmed.
The reports come a day after scores of people were released in Baghdad after being kidnapped by gunmen wearing the uniforms of Iraqi security officers.
Earlier on November 16, gunmen killed at least seven people in an attack on a bakery in eastern Baghdad.
Police say the attack occurred in the Zayuna district of the capital. Customers and bakery staff were among the casualties.
Dozens of bakeries have been attacked in Baghdad in recent months.
A recent wave of insurgent attacks and sectarian violence and has left hundreds of people dead in the city.
Meanwhile, the U.S. military today announced the deaths of two more U.S.soldiers in Iraq. Both soldiers were killed by small-arms fire, one in Diyala Governorate on November 15 and the other on November 14 in Baghdad.
More than 40 U.S. troops have been killed in Iraq this month.
(AFP, AP, Reuters, dpa)