A United Nations team probing the assassination of Benazir Bhutto, a former Pakistani prime minister, has been briefly caught up in violent protests in Islamabad, the Pakistani capital.

Though not the intended target, the UN team was attacked by angry crowds at a protest on Friday against a hike in the price of public transport.

Police fired tear gas to disperse the crowds, which had gathered in two areas in the capital - Bara Kahu and Faizabad, which links to the airport.

The UN team returned to the airport and police sources told Al Jazeera they had demanded security from the US embassy.

Hundreds of people have protested over the increase in public transport costs.

The Pakistani government has already rescinded the fare hike, backing down soon after the protests began on Thursday.

Police said that many of those taking part in Friday's protests were students, demanding the release of demonstrators arrested in the previous protests.

"Yesterday people came out to protest against an increase in transport fares, but today [Friday] they came out with a vengeance, pelting stones at police ... the police had to call in reinforcements," Kamal Hyder, Al Jazeera's correspondent in Islamabad, said.

"Because the rioting is taking place, just on the outskirts of the city straddling a main intersection that  connects other cities to Islamabad and to the airport it is causing huge problems for commuters."