Ofelia Acevedo, second from left, widow of the late Cuban activist Oswaldo Paya, is comforted by an unidentified man in front of the coffin containing her husband's body during a funeral mass in Havana, Cuba, Monday, July 23, 2012. Paya, who spent decades speaking out against the communist government of Fidel and Raul Castro and became one of the most powerful voices of dissent against their half-century rule, died Sunday in a car crash. He was 60. (AP Photo/Ramon Espinosa)
Mourners shout opposition slogans during a funeral mass honoring the Cuban activist Oswaldo Paya in Havana, Cuba, Monday, July 23, 2012. Paya, who spent decades speaking out against the communist government of Fidel and Raul Castro and became one of the most powerful voices of dissent against their half-century rule, died Sunday in a car crash. He was 60. (AP Photo/Ramon Espinosa)
Havana, Cuba – They streamed into Havana to mourn one of their own -- Oswaldo Paya, one of Cuba's leading dissidents, who was killed over the weekend in a car crash.
And the dissidents promised to continue the fight for human rights in their homeland.
Several hundred relatives, friends and fellow dissidents converged on a chapel in the Cerro neighborhood Havana for Paya's wake after his body arrived from the eastern province of Granma.
As the coffin carrying his remains entered, many applauded.
"He was a person sincerely committed to achieving the best for the Cuban people," said Miriam Leyva, one of the founding members of the activist group Ladies in White.
Meanwhile, questions persisted about the circumstances surrounding the crash, with presumptive GOP presidential candidate Mitt Romney and other politicians -- including members of the Cuban-American congressional bloc -- alluding to unconfirmed reports suggesting that another car may have been involved.
Cuban exile groups in the United States demanded a thorough investigation. Paya's relatives have said they believe another car may have tried to run the one carrying Paya off the road. Some dissidents have spread those theories on Twitter and blogs, while others said there was no reason to suspect foul play.
"We rule out any conspiracy theory," said Elizardo Sanchez, a de facto spokesperson for Cuba's small opposition.
Earlier at Paya's home, a close associate gave thanks for what he called an outpouring of support.
"I can promise you and assure you we will continue our struggle, our demands for the civil rights of all Cubans," Ernesto Martini told the mourners.
Paya, 60, gained international fame as the lead organizer of the Varela Project, a signature-gathering drive asking authorities for a referendum on guaranteeing rights such as freedom of speech and assembly. The initiative launched a decade ago was seen as the biggest nonviolent campaign to change the system Fidel Castro established after the 1959 Cuban revolution.
Paya died Sunday afternoon along with another dissident, Harold Cepero Escalante, in the crash in La Gavina, 500 miles (800 kilometers) east of the capital. Authorities said the driver of the rental car carrying Paya and Cepero lost control and struck a tree. Fellow passengers Jens Aron Modig, a Swedish citizen, and Angel Carromero, a Spaniard, were hospitalized with minor injuries and later released.
It was not immediately clear who was behind the wheel.
U.S. President Barack Obama's administration lamented Paya's passing.
Paya was "a tireless champion for greater civic and human rights in Cuba ... (who) gave decades of his life to the nonviolent struggle for freedom and democratic reform in Cuba," the White House said in a statement.
Romney said "the cause of freedom in Cuba has lost one of its strongest voices and respected leaders," and called Paya's death "profoundly heartbreaking and infuriating."
Cuban state media reported the deaths without mentioning that Paya and Cepero were government opponents. Official media rarely refer to dissidents except to excoriate them as "counterrevolutionaries" financed by Washington.
Spanish Embassy spokesman Francisco de Borja said Carromero has been giving statements to investigators and it was unclear when he would return to Spain.
Kalle Back, secretary-general of the Swedish Christian Democratic Youth, said Modig was in Cuba together with Carromero, who's deputy chairman of the Spanish ruling conservative Popular Party's youth wing. The Popular Party said Carromero was in Cuba for vacation and could not say how he came to be traveling in the vehicle with Paya.
Modig is chairman of the youth wing of the Christian Democrats, a small political party that's part of Sweden's center-right coalition government.
"He is doing well under the circumstances," Back said of Modig. "He has been released from the hospital and is under the care of the Swedish Embassy. ... He was there to show his moral support for the democracy movement."
The Spanish government and the European Union, which awarded Paya its Sakharov human rights and democracy prize in 2002, both sent condolences.
"Oswaldo Paya had dedicated his life to the cause of democracy and human rights in Cuba," EU foreign policy chief Catherine Ashton said in a statement.
This story is based on reporting by The Associated Press.