Immigration officers in Beijing have intensified inspections of foreigners as an increasing number have started to use China to enter third countries illegally.

Ji Lixia, assistant head of the Beijing office of China Immigration Inspection, said the number of foreigners being sent back to their home countries has continued to rise in the past three years, but he declined to give an exact figure or the growth rate, citing confidentiality.

Some reports have said that about 200 foreigners were returned to their home countries last year after attempting to enter China without proper documentation.

Since Jan 1, 2013, many Chinese cities, including Beijing and Shanghai, have launched a 72-hour visa-free policy for visitors from some overseas countries who have valid air tickets to a third country.

Most of the foreigners sent home are from developing countries or regions troubled by war and they were returned for staying in China illegally or for disturbing public order, Ji said.

One couple from a war-torn Middle Eastern country was repatriated two months ago.

Zhang Helong, a police officer at the immigration office, said, "They made fake visas and were aiming to use China as a transit country to flee to northern Europe."

Two Iranians on Malaysia Airlines Flight MH370, which went missing on March 8 on a flight from Kuala Lumpur to Beijing, used fake passports and were trying to enter Europe through Malaysia and Beijing.

Job opportunities in China are also attracting many foreigners who do not want to leave when their documents expire.

Zhang cited a case he handled in July.

"The foreigner was from a developed country and he worked as a teacher at a Chinese kindergarten. When his contract expired, the kindergarten didn't rehire him and wasn't in charge of his visa anymore," Zhang said.

"He altered his visa to stay here, but was investigated when he left the country for an emergency," he added.