The soccer World Cup contributed to a 45 per cent gain in advertising fees.

Third-quarter sales would be US$51 million to US$54 million, with advertising revenue forecast at US$31 million to US$32 million or as much as 39 per cent more than a year earlier, the company said.

'Sina will probably achieve this forecast figure because advertising revenue is still growing and the slowdown in mobile wireless business is less than expected,' Richard Ji Weidong, a vice-president of Morgan Stanley, said.

The mainland government recently tightened regulations covering sales of ring tones and other mobile phone services, threatening growth in Sina's wireless value-added business.

Sina could not be certain strong second-quarter revenue growth for ring tone and other wireless services would continue due to the uncertain environment resulting from the regulatory changes, chief executive Charles Chao said.

The shares jumped 17 per cent in after-hours trading to US$24.49 after hitting a 52-week low of US$20.23 on the Nasdaq on Wednesday.

Advertising revenue, which accounted for 54.9 per cent of second-quarter income, was US$29.5 million, higher than the company's forecast of US$26 million to US$27 million and 33 per cent up on the first quarter.

'We have successfully boosted our advertising revenue with the 2006 World Cup which contributed US$8 million in revenue,' Mr Chao said.

The company attracted 57.6 million unique visitors during the competition, a record for Chinese websites, Mr Chao said.

Sina's closest rival, Sohu.com, last week said second-quarter sales rose 36 per cent to US$34.1 million. Advertising revenue rose 35 per cent, also benefiting from the World Cup which started on June 9.

'Sina had previously refocused on its online advertising business and also developed a strong team in reporting sport news, so it benefited the most amongst its peers from the World Cup,' Mr Ji said.

Non-advertising revenue slid 6 per cent to US$24.2 million but still higher than the forecast US$21.5 million to US$22.5 million.

During the second quarter, Sina earned US$2 million from the sale of its stake in a joint venture company formed with South Korean online game company NCsoft.

The new wireless service policies introduced by the government include waivers of some content fees and reminders to customers that they have signed up for subscriptions.

The nation's leading mobile-phone carrier, China Mobile, has started longer free-trial periods for customers of wireless services such as games and tones sold by Sina and Sohu and their competitors.

The rules could have a 'significant' negative impact on wireless revenue for the third quarter, Sina said.

The firm's sales to handset users could fall as much as 30 per cent, according to a Piper Jaffray note last month.