Manama, Bahrain (CNN) -- Police deployed in force throughout the capital city on Tuesday, firing tear gas and making arrests as hundreds of activists tried to reach the landmark Pearl Roundabout on the anniversary of last year's pro-democracy protests in Bahrain.
On Twitter, the Interior Ministry said police had arrested rioters who were blocking a major road in Manama. The ministry also said "thugs" had set fire to an electrical facility in Mughsha, in northern Bahrain, and tried to stop firefighters from putting the fire out.
In Sanabis, on the outskirts of the capital, police fired rubber bullets, bird shot and tear gas at protesters, injuring some. The protests lessened in intensity as the day went on, but small groups of protesters continued sparring with security forces into the evening.
"The country has changed forever since last year," said Jasim Husain, a former member of Bahrain's parliament and a member of the opposition group Al-Wefaq. "This is a new Bahrain. Democracy is the only thing that could bring this popular movement to an end."
The Bahrain Human Rights Center said at least 70 and possibly more than 100 people were arrested in Tuesday's demonstrations, including the center's president, Nabeel Rajab. Among those arrested were six Americans from the human rights group Witness Bahrain, whom the group said police appeared to have targeted specifically.
Bahrain's official information agency said the Americans were swiftly deported for filing false immigration paperwork. The agency said they were "participating in illegal demonstrations" after applying for tourist visas and "agreed to leave the country without further legal procedures."
"People coming to visit Bahrain need to understand that lying on immigration documents is against the law and they will face the consequences of their actions," the information agency quoted an unnamed immigration official as saying.
Two other Americans from Witness Bahrain were deported over the weekend after being arrested at an earlier demonstration, the group said.
The clashes come a day after police used tear gas and rubber bullets on protesters who wanted to march from a Monday night demonstration on the outskirts of Manama toward the roundabout, which became a focal point for protests last year. In Washington, U.S. State Department spokeswoman Victoria Nuland urged both sides to exercise restraint.
"The Bahraini government and the peaceful opposition have a responsibility, both of them, to work together to ensure that the right to peaceful protest is respected by all sides and in this regard we also call on protesters to refrain from violence and we urge Bahraini security forces to use maximum restraint," she said in a briefing for reporters.
Bahrain is a longtime U.S. ally in the Persian Gulf and houses the headquarters of the U.S. Fifth Fleet.
Opposition groups said Monday they are conducting peaceful protests and warned that confrontations "would provide officials a scapegoat for not meeting legitimate demands of the people."
"The political societies consider dialogue as a strategic choice, something offered (a) long time ago," they said. "However, any dialogue not meeting basic demands, such as people being the sources of all power, and not institutionalizing democracy, is pointless and not feasible."
Husain, who resigned his public office over last year's clampdown, said police "made some mistakes" Tuesday. He said they used an excessive amount of tear gas and beat protesters "in broad daylight," but were less abusive than they were in 2011.
"I credit that to training and understanding that there is no point in authorities being harsh with protestors," he said. But he called the deportation of the American activists "quite shameful."
"They are strong believers in democracy," Husain said. "They sacrificed so much to leave their countries and come to Bahrain. They should be appreciated and thanked."
Last year's protests began amid the Arab Spring uprisings across the Middle East and North Africa. Bahraini authorities quickly clamped down on the demonstrations, even demolishing the landmark Pearl Monument that stood in the roundabout. They were aided by Saudi Arabia and the United Arab Emirates, which sent about 5,000 troops to shore up their neighboring kingdom.
In a November report, a commission set up by Bahraini King Hamad al-Khalifa accused police of using excessive force and torture against civilians arrested during the clampdown.
Bahrain's Sunni Muslim monarchy blamed Iran for stirring up protests among its largely Shiite population, but an independent commission that investigated Bahrain's response to the demonstrations found no link to the Shiite-dominated Islamic republic on the other side of the Persian Gulf.
CNN's Samira Said contributed to this report.