Efforts to combat illegal entry and overstaying, especially from neighboring countries, will be strengthened, including building more repatriation centers, a senior official said on Wednesday.

Yang, from the ministry of public security, said tackling illegal employment and overstaying faced difficulties and border police may need language training.

The number of holding centers for foreigners found to have entered the country illegally will be increased, especially in the cities where there is a growing problem, he said.

Foreigners who work without an authorized permit in China are mostly language teachers and domestic helpers, while most illegal entrants come from "neighboring countries", Yang said as he addressed lawmakers during the top legislature’s bimonthly session.

There were about 20,000 instances of illegal entry, employment and overstaying, in 2011, twice as much as in 1995.

Arrivals and departures of foreigners reached more than 54 million in 2011, rising 10 percent annually over the previous decade.

Wu Sicai, deputy director of the arrival and departure division of the provincial public security department in Yunnan, said the province, that borders three countries, has one of the highest numbers of illegal entrants and instances of overstaying.

The southwest province borders Vietnam, Laos and Myanmar and has a border of 4,061kilometers.

Yunnan is an attractive destination as there are few natural barriers, such as rivers, and is culturally close to its neighbors, Wu said.

His office apprehended more than 6,000 illegal foreign employees in 2011, most of them seeking a daily rate of about 30 yuan ($4.8).

"But to send them back can cost several thousand yuan per person," he said.

Wu said there is no repatriation center in Yunnan, but the bureau is planning to build one this year.