Activists said security forces shot dead four people elsewhere, including one in the Damascus district of Midan.
Hama, 200 km (125 miles) north Damascus, has seen some of the biggest demonstrations against Assad and was also the site of a brutal crackdown by his father nearly 30 years ago. Assad deployed tanks outside the city this week.
Live footage on the Internet showed a huge crowd in Hama’s Orontes Square, some of them carrying a long Syrian flag.
In a symbolic show of solidarity, US Ambassador Robert Ford and French ambassador Eric Chevallier visited Hama to put pressure on Assad not to crush the protest.
Ford’s visit was condemned by Syria as incitement and proof that Washington was playing a role in 15 weeks of unrest which have challenged Assad’s grip on power.
The Interior Ministry said Ford met “saboteurs and incited them to violence, protest and rejection of dialogue” which authorities say will be launched on Sunday.
In a now familiar pattern of defiance, protesters emerged from mosques to protest in the capital, the southern city of Daraa where protests first erupted, the industrial city of Homs and other towns nationwide.
Prominent rights campaigner Ammar Qurabi said security forces shot dead three people in Maarat Al-Numaan on the eastern edge of Idlib province, and another was killed in the central Damascus district of Midan.
Residents and activists said security forces shot at protesters at the northern entrance of Hama who were trying to join the demonstration in the city, injuring two people.
US State Department spokesperson Victoria Nuland said Ford’s visit aimed “to make absolutely clear with his physical presence that we stand with those Syrians who are expressing their right to speak for change.”
“We are greatly concerned about the situation in Hama.”
French foreign ministry spokesman Bernard Valero said ambassador Chevallier’s trip was one of several he had carried out to monitor the unrest.
“France recalls its concern for the inhabitants of Hama and its condemnation of the violence in Syria perpetrated by authorities against protesters,” he said, calling on Assad to free political prisoners and launch reforms.
The 1982 Hama massacre came to symbolize the ruthless rule of the late President Hafez Al-Assad. A generation later, activists said security forces shot dead at least 60 people during protests there on June 3.
That triggered an apparent withdrawal of security forces, emboldening protesters who gathered in ever larger numbers after weekly Friday prayers, but also prompting Assad to send security forces into Hama this week as tanks ringed the city.
Hama residents said the US ambassador toured the Hourani hospital where some people were taken for treatment this week during the security crackdown in which activists say security forces killed at least 26 people.
Activists say Bashar’s forces have killed at least 1,400 civilians nationwide in the unrest. Authorities say 500 police and soldiers have been killed by “armed groups” whom they also blame for most of the civilian deaths.
The official Syrian news agency SANA said one member of the security forces was killed in Talbiseh, near the city of Homs, another was wounded in the Damascus district of Midan.
Syria has barred most independent media from operating inside the country, making it difficult to verify accounts from activists and authorities.
It has also largely shut out the United Nations. Secretary General Ban Ki-moon urged Damascus on Thursday to give UN aid workers immediate access to evaluate the needs of civilians caught up in the crackdown and to allow a team of UN human rights investigators to carry out their mission in Syria.
Alongside the crackdown on protests, Assad has promised political reforms and a national dialogue with the opposition, due to start with preliminary talks on Sunday.
But opposition figures have said they will not talk with authorities while the killings and arrests continue.
“I wonder how the authorities could issue an invitation for dialogue when the chains of their tanks are ploughing the lands across Syria, blood is being shed, the jails are flooding with prisoners and Syrians are clamouring to become refugees in foreign lands,” dissident Haitham Al-Maleh said.
“I do not think that any citizen who honors his country would accept such an invitation,” said Maleh, a lawyer and former judge who spent his professional life resisting the takeover of the judiciary by the ruling Baath Party.