Bahrain has denied visa to 54 foreigners who arrived recently in Manama without any invitation from the government, while 12 others were deported for taking part in illegal protests, the interior minister said Monday.

Bahrain has tightened the "visa upon arrival" system after some Western nationals earlier this month arrived in the country and took part in illegal anti-government protests, the Interior Minister Shaikh Rashid bin Abdullah Al Khalifa said.

"Bahrain grants visas on arrival to expatriates from 36 countries. However, as some of them misuse the streamlined visa procedures amid mounting terror threats, we have stepped up entry procedures without affecting the travellers' freedom of movement or the smooth flow of investments," the minister said.

Late last week, four more foreign "activists" participating in unauthorized protests in Bahrain have been deported for cheating on immigration forms.

Besides, Bahrain on last Tuesday deported six American activists who applied for tourist visas under false pretenses and participated in illegal demonstrations, after two U.S. nationals were detained and then deported for the same reason.

Bahrain has been witnessing more demonstrations to mark the first anniversary of the anti-government protests on Feb. 14. Activists have been visiting Bahrain as tourists to attend protests through the visa facility.