Bahraini police have fired tear gas and stun grenades to disperse protesters trying to march to Pearl Roundabout, the now-crushed symbol of the pro-democracy uprising that began nearly two years ago.

Hundreds of people marched towards the square in the capital Manama carrying Bahraini flags and chanting, "square of martyrdom, we all still have the will."

The protest was called by the February 14 coalition, a loosely-organised group of mostly young protesters.

"Down with the corrupt government," the demonstrators chanted. "Khalifa resign," they called, referring to the king's uncle Prince Khalifa bin Salman, who has been prime minister for four decades.

The prince is the longest-serving prime minister in the world, and a particularly reviled figure among Bahrain's opposition.

The interior ministry said on Twitter that after the opposition's rally ended, "a group of saboteurs caused [a] riot and blocked roads, requiring authorities to take legal action against them."

Tense time in Bahrain

The protesters who tried to march to the square broke off from a larger rally organised by Al Wefaq, the main opposition party, in the village of Sanabis just outside the capital.

Opposition supporters have been demonstrating for more than a week ahead of the anniversary.

Protesters camped at Pearl Roundabout for nearly a month in early 2011 before they were forcibly expelled in mid-March. Authorities later razed the iconic statue at the centre of the square.

More than 80 people have been killed in the unrest. The government set up an independent commission to study the unrest. Its report, released in late 2011, documented the excessive use of force against mostly peaceful protesters.

Bahrain says it has implemented the report's recommendations, but the opposition says that abuses continue, with regular reports of torture and the widespread use of tear gas in villages.

A new round of "national dialogue," organised by the government, began on Sunday; it includes representatives from Wefaq and other opposition groups, plus members of pro-government groups like the National Unity Gathering and the salafi Asala party.

Officials have revealed little about the substance of the talks so far.

The opposition has continued to press for major political reforms, including a constitutional monarchy and an elected prime minister.