Australian captain Steve Waugh carried out his threat to lead his players off the field on Tuesday after a fan threw a firework onto the field during the Australia-Pakistan Tri-Nations game at Trent Bridge.

With Pakistan at 250 for six off 45 overs, a number of fireworks went off in the stands. Supporters scrambled away and stewards and police moved in.

But one of the fireworks, which didn't appear to go off, landed on the field close to fielder Brett Lee and Waugh, who had threatened before the game he would take his players off the field if there was any further misbehaviour after Sunday's crowd invasion at Headingley, led them off.

After an 18 minute delay, during the which the Australians agreed to resume provided there was no further trouble, the match resumed.

The security at Trent Bridge had been beefed to prevent a repeat of Sunday's scenes at Headingley where stampeding Pakistan fans left a steward with broken ribs, a broken nose and a damaged spleen.

More than 350 stewards were on alert and temporary, plastic fences just hung over the advertising hoardings in case anyone decided to run on the field.

The measures have been taken by the local club to avoid a repeat of the two pitch invasions that have marred this 10-match series. After celebrating Pakistan fans ran onto the field at Headingley on Sunday and the steward lay injured on the field, England skipper Alec Stewart took the unprecedented step of conceding the match to Pakistan to for safety reasons.

Steward Stephen Speight, 31, said he had been trying to hold on to the stumps when he was kicked in the face and chest by a group of fans.

"My head felt like it had just been kicked around a football field," Speight said.

In an emergency the plastic fences will be hoisted by the stewards to stop the invading spectators and anyone caught running into the field will be arrested, according to the local chief executive David Collier.

Thousands of Pakistan fans, who appear to have outnumbered the Australian support, made it virtually a home match for their side, sounding horns and creating the sort of atmosphere that has become a typical Pakistan games in this series.

There had been no trouble until the fireworks went off in the Radcliffe Road stand housing most of the Pakistan fans. Most of the fans moved away from the area where they were going off and some were cowering in their seats.

Waugh took his players off while the two Pakistan batsmen, Rashid Latif and Azhar Mahmood, initially stayed out on the field before they also left the field.

© 2001 AAP