China has pledged to invest $57 billion in Pakistani road, rail and power infrastructure in a flagship project of its vast Belt and Road initiative for a network of modern-day "Silk Road" routes connecting Asia with Europe and Africa.
China's ambassador to Pakistan and other officials have often urged Islamabad to improve security, especially in the province of Baluchistan, where China is building a new port and funding roads to link its western regions with the Arabian Sea.
Anwar ul Haq Kakar, a Baluchistan government spokesman, said men pretending to be police officers kidnapped the Chinese teachers and wounded a passerby who tried to stop them.
"A Chinese couple has been kidnapped," Kakar told Reuters, adding that officials had earlier mistaken the wounded passerby for a security guard.
"(The passerby) inquired why they were doing this and they said they were from a law enforcement agency, but when he asked for their identification cards, they shot him," added Kakar.
No group has claimed responsibility for the kidnapping, but in the past Islamist militant groups have kidnapped foreigners in Pakistan to seek ransom or drum up publicity for their cause.
China's embassy in Islamabad confirmed two of its nationals had been kidnapped, Chinese state news agency Xinhua said.
China's foreign ministry did not immediately respond to a faxed request for comment sent after office hours.
Quetta police chief Razza Cheema said the teachers did not work on the Beijing-funded China-Pakistan Economic Corridor (CPEC) as they did not have guards. Pakistan provides security for all Chinese workers on CPEC projects in Baluchistan.
"Armed men took the couple into custody at gunpoint when they were coming out from the centre," Cheema told Reuters.
Another Chinese woman narrowly evaded the kidnappers outside a language centre in Jinnah, on the city's outskirts, he added.
The numbers of Pakistanis studying Mandarin has skyrocketed since 2014, when President Xi Jinping signed off on the vast CPEC funding plans.
Security in Baluchistan has improved in recent years but separatists, who view the project as a ruse to steal natural resources, this month killed 10 Pakistani workers building a road near the new port of Gwadar.
Pakistan faces pressure to keep Chinese workers safe and reassure Beijing about its vast investments, said Vahaj Ahmed, a research analyst at investment bank Exotix Partners.
But the Quetta kidnappings were unlikely to "put the Chinese interests off track," he added.