A Reuters witness said seven people had been arrested after police and security forces on horseback tried to push back an estimated 1,000-strong crowd. Indian television stations said the protests had been related to government jobs in Punjab.
Wednesday's match is the first between the two neighbours in India since Pakistan-based militants killed 166 people in the 2008 Mumbai attacks. The winners will play the victors of Tuesday's Colombo semi-final between Sri Lanka and New Zealand in Mumbai on Saturday.
In Karachi, Interior Minister Rehman Malik warned the Pakistan team they were being kept under a close scrutiny because of the recent spot-fixing scandal.
"We are taking no risks now and we are keeping a close watch on the team for the semi-final because we don't want any more spot-fixing scandals," Malik told reporters.
Three Pakistan players have been banned for a minimum five years each for manipulating incidents in last year's Lord's test against England.
Former Pakistan captain Imran Khan told Indian television channels he was appalled by what Malik had said before such an important match.
"I just hope he didn't mean what he said as it is not good for the team," Imran said.
Pakistan pace bowler Umar Gul told a news conference he had not heard the minister's remarks.
LOT OF SCANDALS
"We are just focusing on the game and there is no pressure on us," he said. "For the past five to six months, we have endured a lot of pressure and scandals. But we have been doing well for some time."
Wednesday's match has overshadowed the Colombo semi-final where Muttiah Muralitharan is an injury doubt.
Muralitharan, 38, the leading wicket-taker in both test and one-day internationals, will retire from international cricket after the tournament. He is suffering from a bruised knee and a quadriceps injury and left the field early in Saturday's quarter-final win over England.
"This is the crunch game and, if he can play tomorrow, that will be great for us. But if that doesn't work out for us we have got enough cover to make sure that we are still a solid winning side," captain Kumar Sangakkara told a news conference.
"We will have to just monitor how he goes and hope he is fit enough to play.
