ISTANBUL (CNN) -- Riot police fired tear gas and water cannons Wednesday at hundreds of protesters trying to hold May Day demonstrations in Istanbul's iconic Taksim Square in defiance of a ban.

The clashes came as police locked down all roads leading to Istanbul's main commercial district, after barring the annual Labor Day rally in Taksim Square for the first time in three years.

Despite the shutdown, riots raged throughout densely populated parts of central Istanbul as demonstrators tried to reach the traditional May Day rally site.

Activists and government officials traded accusations about who was responsible for the tensions.

Istanbul Gov. Huseyin Avni Mutlu said 22 police officers were wounded from rocks and other objects thrown at them.

"We carried out a tremendously even-handed intervention," he said.

Mutlu said police detained 72 protesters in connection with the day's events. Three protesters were injured, all of whom were members of "marginal" leftist groups, Mutlu said.

But human rights organizations said that number did not reflect the real number of people injured and accused police of recklessness.

"It is irresponsible for the governor to make these kinds of statements about the number of people injured," said Umit Efe, head of the Istanbul branch of the Human Rights Association of Turkey.

"We are still gathering the numbers, but in just one hospital, we see 40 people have been admitted, mostly for head traumas and respiratory problems," she said. "So many gas bombs were thrown in Istanbul today, we should be looking at this from the viewpoint of attempt on life."

According to the Human Rights Association of Turkey, a 17-year-old activist is in critical condition after a gas canister hit her in the head at close range. Video footage showed the young woman collapsed on a sidewalk amid a growing cloud of tear gas.

Seconds later, police rushed to the fallen girl, who was later taken to a hospital.

Authorities say they refused to grant permission to trade unions and youth groups for demonstrations in Taksim Square because of a large-scale construction project in the area.

But unions and youth groups say that the square is the historic site of May 1 activities and that they have a right to demonstrate there.

City shutdown

In a move that few Istanbul residents recall seeing before, authorities removed part of one bridge and raised a bridge over an estuary in an apparent effort to block demonstrators from approaching the traditional rallying ground.

Groups carrying May 1 international workers' day banners and chanting "Long live Workers' Day" as they sought to get to the square were dispersed using water cannons and tear gas in the city's Besiktas district.

Meanwhile, Istanbul is under a citywide shutdown. Authorities have closed roads and suspended public transportation to the square, including subways, buses and the ferry services that carry passengers between the city's European and Asian sides.

Youth groups have been canvassing Istanbul with posters that read, "Bring your anger, and come to Taksim."

Thirty-four people were killed on May 1, 1977, in Istanbul when gunmen fired on demonstrations during a time of political upheaval in Turkey. Later, the 1980 junta declared May 1 celebrations illegal in Taksim Square.

The May 1 demonstrations of the past three years took place under a heavy police presence.