| Bahrain's ruling Al Khalifa family, from the minority Sunni population, has declared martial law [GALLO/GETTY]
Police have broken up small scattered protests in Manama, Bahrain's capital, using tear gas after calls for a "Day of Rage" were quashed by a heavy security force presence.
Helicopters, extra checkpoints on major highways and visible security forces appeared to have prevented any major demonstrations from gathering support.
A 71-year-old man died of asphyxiation in his home after police fired tear gas in the village of Mameer, the main Shia protest group said.
Al Jazeera's correspondent in Manama said: "As far as we can see there are clouds of tear gas that have been rising in recent minutes.
"People will march down the streets and a helicopter will appear, the police will move in, and people move indoors.
"Quite a tense situation here, but the call for the big protests ... seems to have been quashed by the authorities here.
"Some protesters tried to mess with the statue and at that point the police opened fire."
At least 20 people have been killed, including two policemen, during a month of demonstrations against the Sunni-led government.
In Maameer, Wefaq, the country's leading Shia opposition group, said 71-year-old Isa Abdullah had died of suffocation as tear gas fumes leaked into his house.
"His village Mameer was attacked heavily by tear gas," said Mattar Ibrahim Mattar, the Wefaq leader. "His family called the emergency room but there was no response from Salmaniya hospital."
A statement from Wefaq said Mameer had been blockaded by police forces and a lack of hospital assistance made it impossible to revive Abdullah.
It said there was no indication he had been involved in the protests.
Wefaq, which draws tens of thousands when it calls protests, had distanced itself from Friday's of "Day of Rage".
"Wefaq affirms the need to protect safety and lives and not to give the killers the opportunity to shed blood," it said.
Confronted by mass protests demanding constitutional reform, Bahrain's ruling Al Khalifa family, from the minority Sunni population, has declared security their priority, calling in troops from neighbouring Sunni-led Gulf states and imposing martial law.
A few hundred protesters managed a short rally in the Shia village of Diraz on Friday, shouting "down with the regime" as women swathed in black waved Bahraini flags and held up copies of the Quran.
But they fled when about 100 riot police fired tear gas and tried to chase them down.
In the village of al-Dair, police fired rounds of tear gas to disperse about 100 protesters who had marched toward a main road next to a runway at Bahrain International Airport.
Residents in nearby streets rushed women and children into their house as police continued to use tear gas.
The residents said police had also fired birdshot ammunition at protesters.
"After so many deaths, so many sacrifices, we will continue to protest. We just want a new constitution but they're not prepared for democracy," one resident said anonymously.
Al Jazeera's correspondent in Manama said: "There was a big police presence this morning that moved in and around these [Shia] villages, stopping people from going to prayers.
"It seems in the last hour or so those protests have actually begun, and police have started moving into these villages."
More than 60 per cent of Bahrainis are Shias and most are demanding a constitutional monarchy.
But calls by hardliners for the overthrow of the monarchy have alarmed Sunnis, who fear the unrest helps Iran, a mainly Shia country, on the other side of the Gulf.
In signs of rising tensions in the oil-producing region, Bahrain's government has responded sharply to any signs of what it considers to be interference over its crackdown.
Last week, Bahrain expelled diplomats from Iran after Tehran criticised the last week's clampdown on protesters.
The foreign minister of Bahrain has formally complained to the Lebanese government over expressions of support from Hezbollah, a Shia movement.
Bahrain's social development minister accused demonstrators on Friday of harbouring a "foreign agenda", but stopped short of blaming Iran.
"We found out that those people who were doing it were instigated by a foreign country and by Hezbollah," Fatima al Beloushi told a news conference in Geneva.
"We have direct proof. Hezbollah has provided training for their people. They were serving a foreign agenda and that is why it was not something for having a better livelihood."
Bahrain has great strategic importance because it hosts the US Fifth Fleet, facing Iran across the Gulf and situated off-shore from Saudi Arabia, the world's top oil exporter.
Source: Al Jazeera and agencies