LONDON (Sapa-AP) - Britain took new measures Monday to protect itself against the changing tactics of violent Islamic extremists by requiring visas for South Africans and other foreign nationals.

Home Secretary Jacqui Smith said South Africans will now need to apply for visas to enter Britain, tightening the entry process into the country for some 420,000 South Africans who visit each year. South African passports had previously allowed visa-free travel into Britain.

British security and intelligence officials have warned of an increasing risk from Islamic extremists using South Africa as a transit point and planning plots there.

They have said future attacks on Britain could be directed from countries other than Pakistan - where dozens of Britons with family ties have traveled for terrorist training or have been linked to recent terror plots.

"We are completing some of the biggest ever changes to strengthen Britain's border security," Smith said Monday.

A British security official, who requested anonymity to discuss national security issues, said Britain's government has specific concerns about terrorists seeking to evade law enforcement by using South Africa as a transit point to enter the U.K.

Officials have said terrorists and criminals are exploiting the availability of stolen or forged South African passports to gain access to Britain and other countries.

Siobhan McCarthy, a spokeswoman for South Africa's Home Affairs ministry, said steps have been taken to prevent corrupt officials issuing bogus passports, and to make the documents harder to copy.

Stephen Lander, the head of Britain's Serious Organized Crime Agency and the ex-director of the country's domestic intelligence agency MI5, has warned lawmakers that new restrictions are needed to stop the flow of people illegally entering the country via South Africa.

Lander said problems with forged South African passports were exposed in a major 2006 investigation into people trafficking. Two Britons used fake documents to smuggle around 6,000 illegal immigrants into the U.K., the U.S. and Canada via South Africa. Both men were each jailed for 10 years over the smuggling racket.

"The British government is well aware of the changes we are making to our passport and ... other changes that the department is implementing to improve the security and the integrity of our documents," McCarthy said. She said South Africa would issue a new type of passport next month.

Sajjan Gohel, director of international security at the London-based Asia-Pacific Foundation, said there had been an increase in South Africans with ties to Pakistan traveling there and warned that the radical Muslim group Tablighi Jamaat is winning a large following in South Africa's coastal city of Cape Town.

"It is a very good and very convenient terrorist hub where extremists can plot and plan and then move on to carry out attacks," Gohel said.

Prosecutors in the London trial of several men accused of plotting to blow up at least seven trans-Atlantic airliners said last year that a suspect had flown into Britain from South Africa to lead the final stages of the plan.

Mohammed Gulzar traveled to Britain from South Africa via Mauritius in July 2006. Gulzar was acquitted on all charges over the plot, but law enforcement officials said the case highlighted the potential for terror suspects to transit through South Africa. A retrial is scheduled for later this month.

Officials say they are also investigating new threats from Bangladesh. Bangladeshis already need to apply for visas to travel to the U.K.

Last April, Smith visited Bangladesh to discuss closer cooperation following concerns that British Muslims with ties to the country could begin pose a similar threat to those with links to Pakistan. The two countries are working jointly on programs aimed at preventing radicalization.

Maj. Gen. A.N.M. Muniruzzaman, a former adviser to the Bangladesh government, said the threat posed by extremists in Bangladesh was real but not being taken seriously.

"That's still the case and it's very wrong," Muniruzzaman said.

Smith said Monday that visitors from Bolivia, Lesotho, Swaziland and Venezuela would also need visas in the future, because of concerns over crime and illegal immigration. She said the new visa requirements will come into effect by mid-2009.

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