LONDON — The pit at the International Petroleum Exchange fell silent for good Thursday, as the noisy practice of traders in multicolored jackets shouting orders and using hand signals was banished in favor of a fully electronic system.

The switch to screen trading of oil futures contracts, which brought an end to the 25-year tradition of open outcry trading, is part of the IPE's plan to improve efficiency and competitiveness.

But the move has also prompted a renewed attack from the New York Mercantile Exchange. The world's biggest energy futures market has set up a rival exchange in Dublin that it plans to move to London, pledging its commitment to retain an active trading floor.

"Coming soon to London, a champion of open outcry trading," the Nymex trumpeted in a carefully timed half-page advertisement in the Financial Times on Thursday. "Our floor will be fitted with the latest in technology — humans."

The Nymex's campaign received a further boost when a technical hitch interrupted trading on the IPE for an hour and a half during Thursday morning's electronic session. Traders said an attempt to restart the system failed. The IPE declined to comment Thursday.

"It's a subdued atmosphere in here today; it really is the end of an era," said a trader who did not want his name used. "The electronic outage earlier doesn't help the feeling on the floor, and there'll be a few people making the weekly commute to Dublin for trading."

The Nymex, meanwhile, made that journey easier for many traders — throwing a reception at a pub across the road from the IPE after the traders left the pit for the last time after Thursday afternoon's session.

Nymex spokeswoman Anu Ahluwalia said the gathering was an informal way of saying "we are there for them." About 220 pit traders are directly affected by the IPE's decision, and could lose their jobs.

The Nymex is also offering substantial financial assistance for traders who make the switch to Dublin, which offers an alternative to the IPE's benchmark North Sea Brent contract — providing expenses of $1,000 a week or stipends of $100,000 a month in some cases. Ahluwalia said the Dublin operation has attracted more than 150 traders so far.

The Nymex said in March it had signed a lease on a headquarters in central London, but it has not yet registered with the Financial Services Authority for regulatory approval, citing the size of the application. The British watchdog has said the subsequent approval process could take four to six months.

Analysts said the competition between the two exchanges will come down to the debate over open outcry and electronic trading.

Supporters of electronic trading believe cutting the need for a physical presence at the IPE will allow a trader to work in any number of markets from any location. They also claim that on-screen trading ensures a more transparent and easier to regulate market.