Online betting shares have been hit by legal action in the US

Revenues were up 50% to $319.3m (�172.7m) in the three months to June, from $214.8m the previous year.

The results come amid a crackdown on internet gambling in the US, which has triggered turmoil in the industry.

Some 73% of Partygaming's revenue still comes from the US, although the firm says almost half its 232,446 real-money poker signups came from elsewhere.

The renewed US determination to tackle what it sees as illegal online gambling follows the arrest in Dallas of the boss of a rival gaming firm.

Betonsports' chief executive, David Carruthers, was arrested for racketeering earlier this week after being named in an indictment - along with 11 other people and three other companies.

Mr Carruthers is due to have his bail hearing in the US later on Friday afternoon.

"In the midst of this turmoil, Partygaming is accelerating its strategy to become less reliant on US income - already this figure has reduced to 73% of total income, as opposed to 90% at the time of its initial float last year, " said Richard Hunter, analysts with Hargreaves Lansdown Stockbrokers.

Expansion

Continuing to drive international expansion remains a clear objective over the coming months Mitch Garber, Partygaming chief executive officer See Partygaming's shares

The firm aims to pursue the growth of its non-US business "aggressively", particularly in Europe and South America.

"Continuing to drive international expansion remains a clear objective over the coming months," said Mitch Garber, the firm's chief executive officer.

As well as expanding geographically, the firm plans to add new games during the fourth quarter.

While Partygaming sales have risen, the yield per active player has actually fallen to $17.40 compared to $18.50 in the quarter before, although this is 2% up on the same period of 2005.

The amount gambled in its casinos declined from �4.47bn to $4.13bn from the previous quarter in part due to less being gambled on blackjack.

In early trading on Friday the firm's share price was 89 pence, considerably less than the firm's offer price of 116p.