Nigeria has increased the minimum capital required for domestic and international airlines by between 25 and 100 times after two crashes last year exposed serious problems in the industry, an official said on Wednesday.

The government has increased the capital base requirement for domestic airlines 25-fold to 500 million naira (USD$3.9 million), regional airlines 50-fold to 1 billion naira (USD$7.8 million) and international operators 100-fold to 2 billion naira (USD$15.6 million), Aviation Minister Babalola Borishade said.

"These deposits... will be used to control access to the aviation industry," Borishade told reporters after a cabinet meeting in the capital Abuja.

The measure takes effect in March 2007.

The new capital requirement comes after two major crashes last year that killed 223 people, calling into question the safety of Nigeria's aviation industry. There has been no official report on the causes of either crash.

The minister said cabinet also approved 19.5 billion naira in funding to improve safety at airports in the world's eighth biggest oil exporter, which had been announced previously.

Borishade said last month that 6 billion naira of the total amount would go towards upgrading the air traffic control tower at Lagos Airport, the busiest in Africa's most populous country where air traffic amounts to 8 million passengers a year.

The funding will also allow for the renovation of the second runway at Lagos. At present there is only one functional runway for both international and domestic flights.

Most Nigerian airlines have ageing fleets, and maintenance and operational procedures are often inadequate to ensure passenger safety, the US State Department said in a travel warning in January.

Last October an aircraft operated by private carrier Bellview crashed shortly after take-off from Lagos, killing all 117 people on board. It took authorities 15 hours to locate the crash site.

On December 10, a plane flown by another private airline, Sosoliso, crashed at Port Harcourt Airport, killing 106 people of whom half were schoolchildren going home for Christmas. The plane burned on the runway because there were no functional fire engines at the airport.

President Olusegun Obasanjo ordered urgent reforms after the Sosoliso crash and several airlines were temporarily grounded while their fleets were inspected.

Obasanjo said at the time that corners were being cut in every part of the industry.