Police in Nepal have detained 122 Chinese nationals in its biggest crackdown on crime by foreigners entering the country on tourist visa, officials said.

The chief of police in the capital, Kathmandu, Uttam Subedi, on Tuesday said 122 Chinese men and women were rounded up in raids on Monday following information that they were engaged in suspicious activities.

The Chinese are suspected of carrying out cyber crime and hacking into bank cash machines, Subedi said, adding that they were being held in different police stations and their passports and laptop computers had been seized.

"This is the first time that so many foreigners have been detained for suspected criminal activities," he said.

Chinese embassy officials were not immediately available for comment but another senior police officer, Hobindra Bogati, said the embassy knew of the raids and had supported the detention of the suspects.

Chinese people are regularly detained in Asian countries on suspicion of involvement in various illegal activities, often involving fraud back in China.

Police were also investigating if they had violated immigration laws by overstaying their visas.

Last week, authorities in the Philippines arrested 342 Chinese workers in a raid on an unlicensed gambling operation.

In September, police arrested five Chinese nationals on a charge of stealing money by hacking bank cash machines. Chinese citizens were also arrested with smuggled gold this year.

Nepal and China signed a treaty on mutual assistance in criminal matters during a visit to Nepal by President Xi Jinping in October.

China has been increasing its investment in Nepal in recent years in areas such as roads, power plants and hospitals.

More than 134,000 Chinese tourists visited Nepal between January and October this year, up 9.2 percent from the same period in 2018, according to Nepal Tourism Board data.