Spain on Friday mourned two police officers who were killed by suspected Basque separatists on Majorca island, with royals presiding over a state funeral mass, and thousands of people demonstrating against the bombing, according to dpa. Police meanwhile identified two suspects who were believed to be still on the island, media reported. The Interior Ministry made public the photographs of six suspected members of the militant Basque separatist group ETA, who were believed to be involved with the group's current offensive. Police officers Carlos Saenz de Tejada, 28, and Diego Salva Lezaun, 27, were killed Thursday when their car exploded in the tourist resort of Palmanova in the west of the island. Crown Prince Felipe, his wife Letizia, Interior Minister Alfredo Perez Rubalcaba and other dignitaries attended a solemn funeral mass at Palma cathedral. Earlier, Prime Minister Jose Luis Rodriguez Zapatero had visited a funeral chapel for the slain officers of the paramilitary Civil Guard, decorating them posthumously for bravery. Thousands of people around Spain held silent rallies to condemn the killing. Thursday's attack followed a car bombing which caused slight injuries to about 60 people in the northern city of Burgos on Wednesday. Police were carrying out tight controls at Majorca airport and ports in a hunt for two suspects who were believed to be still on the island, according to media reports. They could be a Basque-speaking couple that rented a hotel room in Palma and disappeared on Thursday, national radio RNE reported. Sea traffic in the ports of Palma and Alcudia remained limited as no vessels were allowed to depart without authorization, port authorities said. Air traffic meanwhile largely returned to normal after Majorca airport was closed for nearly two hours after Thursday's attack, causing delays. The bombers were believed to have attached explosives to the police vehicle that blew up. The explosion occurred just a few hundred metres from the beach in Palmanova, which is one of Majorca's main tourist resorts. The British Foreign Office warned of "a high threat of terrorism in Spain" on its website, saying that "indiscriminate" attacks could occur in places frequented by foreign travellers. Tourists on Majorca, however, returned to the beaches, and local tourism professionals insisted the island was safe. Thursday's attack was an "absolute exception," Alvaro Middelman of the local tourism professionals' association Fomento de Turismo told the German Press Agency dpa. "I would say the island is as safe as it always was," he insisted. "The attack did not target tourists, but the police," Balearic Islands regional Tourism Minister Miquel Nadal said. King Juan Carlos and Queen Sofia did not cancel their plans to vacation on Majorca from Saturday onwards. The attack occurred at about seven kilometres from Marivent palace, where the royals traditionally spend their summer holidays. ETA made unsuccessful plans to kill the king on Majorca in 1995. The Spanish government had braced for attacks as ETA marked its 50th anniversary on Friday. Zapatero urged police to intensify its fight against ETA and to improve protection measures for its officers. The security forces needed to be on high alert even though ETA was "ever weaker," said Jose Antonio Alonso, a spokesman for Zapatero's Socialist Party. ETA, which is listed as a terrorist organization by the European Union and the United States, has killed more than 800 people in its campaign for a sovereign Basque state. Its attacks have claimed three lives this year, all of them police officers.