Nigeria said on Thursday it was fining airlines British Airways and Virgin Atlantic a total of $235 million (149 million pounds), as an ongoing row between Britain and Africa's most populous nation over landing slots and ticket prices escalates.

Flights between Britain and Nigeria almost came to a halt this week but a last minute deal on Tuesday ensured British Airways, Virgin Atlantic and Nigeria's flagship airline Arik Air continue to fly from London to Lagos and Abuja.

We are charging British Airways $135 million and Virgin Atlantic $100 million for abuse of a dominant position, fixing prices, abusing fuel surcharges and taking advantage of passengers, said Harold Demuren, Director General of Nigeria Civil Aviation Authority (NCAA).

We have been investigating for the last six months. Lagos to London has the highest route yield in the world. Our market is open for exploration, not exploitation.

British Airways said it rejected the Nigerian authorities allegations and it was vigorously defending our position.

We pride ourselves on offering competitive fares, a choice of products and connections to our Nigerian customers, a statement from the airline said. We remain committed to Nigeria and have been flying there for more than 75 years.

Nigeria threatened last month to reduce British Airways flights between London and the West African nation's commercial-hub Lagos to three from seven weekly, after London Heathrow stopped Arik Air flights from the capital Abuja.

A deal this week means all flights will continue until the end of the year when the Nigerian government wants something done about the high ticket costs on British airlines.

Nigeria's aviation ministry says British airlines charge far more to fly to Nigeria than to neighbouring Ghana, while it believes Arik Air should not have to pay high costs to land at Heathrow when Lagos airport doesn't charge those fees.

Britain has said that it can't control what private companies who control the airlines and airports charge but it is in constructive dialogue with the Nigerian government.

(Additional reporting by Sudip Kar-Gupta in London; Editing by Jon Loades-Carter and Will Waterman)