Armed tribesmen in Egypt abducted 25 Chinese workers on Tuesday, the second incident in less than a week of Chinese nationals being taken hostage in Africa.
The latest incident has prompted renewed calls to improve security for Chinese workers overseas.
Bedouins, nomadic tribesmen, kidnapped the workers in Sinai to demand the release of relatives detained over fatal bombings in the peninsula between 2004 and 2006, AFP cited a security official as saying.
The workers, technicians and engineers for a military-owned cement factory in the Lehfen area of central Sinai, were abducted on their way to work, the official said.
"The Chinese will not be released until our demands are met," one Bedouin protester told AFP.
The protesters are demanding the release of five Bedouins held in connection with an attack on the tourist resort of Taba in 2004.
They say the ruling Supreme Council of the Armed Forces, which took power last year after president Hosni Mubarak was ousted, has repeatedly promised to release the Bedouins.
A Chinese embassy official confirmed that workers had been kidnapped but did not confirm the number.
"About 20 Chinese nationals" were held by some local people, the embassy official told Xinhua News Agency.
The workers were taking a bus to their plant when they were stopped, the embassy official said.
The workers were being held in a tent in Lehfen, where protesters have been blocking the highway to northeast Sinai for three days, the Bedouins said.
An Egyptian security official said authorities were in talks with Bedouin elders to try to resolve the issue.
It was the second kidnapping of Chinese workers in less than a week. On Saturday, 29 workers were abducted by rebels in Sudan and efforts to secure their release are ongoing.
He Wenping, an expert on African studies at the Chinese Academy of Social Sciences, said on Tuesday that an increasing number of Chinese are working in Africa.
"As Chinese projects in Africa increase, the risk of Chinese workers being kidnapped also rises," she said.
In addition, Chinese workers generally have a poor awareness of security in Africa as they tend to take it for granted that their safety can be ensured because of the traditional friendship between China and Africa, she said.