Police in the former Soviet republic of Azerbaijan used water cannons and tear gas Saturday to break up a rally of opposition demonstrators, who were protesting what they say was a fraudulent election two weeks ago. It was the first rally in the oil-rich Caspian Sea nation that ended in violence since the vote.

Hundreds of police in riot gear used water cannons and truncheons to break up the rally, called by the opposition political alliance in Azerbaijan's capital, Baku.

Witnesses reported a number of people were injured.

An estimated 15,000 people gathered in Victory Square to hold a demonstration to demand a rerun of the November 6 election, which the ruling party of President Ilham Aliyev won in a landslide.

Opposition leaders initiated protests soon after the voting, which international observers said failed to meet international standards.

The opposition has since held several protest rallies, all of which ended peacefully.

On Saturday, demonstrators attempted to stay beyond the allotted two-hour time limit, and set up a permanent presence on the square.

When leaders announced the rally would become a sitting protest, the police acted quickly.

They broke up a stand used by the leaders, and tore down banners that were orange, the color borrowed from Ukraine's so-called Orange Revolution that led to a change in government there last year.

After the recent election, the Azeri authorities said fraud had occurred in certain areas, leading to a reversal of results in some cases. But the opposition says this was not enough, and has demanded an entirely new election.

The opposition won just 10 seats in the 125 seat parliament, according to the official results released last week.

In a statement, the U.S. Embassy in Baku strongly condemned what it called "the unjustified and unprovoked use of force against citizens peacefully exercising their right to freedom of assembly," and urged the government to punish those responsible.