A car bomb killed at least 43 civilians and wounded dozens on the Syrian side of the Bab al-Salama border crossing with Turkey on Thursday, a monitoring group said.

Women and children were among the dead in the blast in an area used as a car park, the Syrian Observatory for Human Rights said, updating an earlier toll of 29.

Turkey's biggest union geared for a massive strike on Thursday amid mounting anger over the country's worst mining accident, as the toll from the disaster rose to 282, with scores still trapped underground.

"Those who keep up with privatisation... policies, who threaten workers' lives to reduce costs... are the culprits of the Soma massacre and they must be held accountable," Turkey's Public Workers Unions Confederation (KESK), which represents 240,000 employees, said on its website.

The United States and Israel on Wednesday offered to help Turkey, which was reeling from a mine disaster which killed 245 workers.

"On behalf of the American people, we extend our heartfelt condolences to the families of the victims and our best wishes for the safe exit of the remaining miners," said White House spokesman Jay Carney.

Anger was growing across Turkey on Wednesday as hopes faded for scores of workers trapped in a collapsed mine and the death toll hit 245, edging it closer to becoming the country's worst-ever industrial disaster.

Thousands of protesters took to the streets in Ankara and Istanbul, accusing the government and mining industry of negligence, as Prime Minister Recep Tayyip Erdogan rejected claims of government culpability.

At least five miners were killed and as many as 400 others remain trapped underground after an explosion in a coal mine in the western Turkish province of Manisa on Tuesday, officials said. 

"We have been informed that five people died and 30 people were rescued," said Manisa mayor Cengiz Ergun, as rescue workers tried desperately to reach the trapped miners. 

Turkey said Tuesday it will defy a European court order to pay 90 million euros ($124 million) in compensation to Greek Cypriots over its 1974 invasion of the island.

The European Court of Human Rights ordered Turkey to pay the damages this week, 13 years after finding it guilty of "massive and continuous" rights violations against Greek Cypriots on the island.

Turkish Prime Minister Recep Tayyip Erdogan on Tuesday rejected growing criticism that his government was muzzling the press, saying many Western countries had even worse records on media freedom.

Erdogan's speech to parliament followed a report by the U.S.-based watchdog Freedom House earlier this month, which downgraded Turkey's status from "partly free" to "not free" and said the country had seen the biggest decline in press freedom in Europe.

U.S. Vice President Joe Biden will visit Romania and Cyprus this month, seeking to underscore Washington's commitment to eastern Europe and deepen Russia's isolation over the Ukraine crisis.

"The vice president will discuss with the leadership of both countries the international community's response to Russia's illegal military intervention and destabilizing actions in Ukraine," the White House said in a statement.

The European Court of Human Rights Monday ordered Turkey to pay 90 million euros ($124 million) to compensate Greek Cypriots who suffered discrimination as a result of the 1974 Turkish invasion of Cyprus.

The court said 30 million euros should go to the families of people who disappeared after the invasion, and the rest to enclaved Greek Cypriots on the Karpas peninsula in the north of the divided island under Turkish Cypriot control.

A Turkish court heard testimony on Monday that eight men, including four police officers, pummeled a teenage protester to death with baseball bats and truncheons during anti-government demonstrations last year.

Ali Ismail Korkmaz, 19, died after being repeatedly beaten during protests in the western city of Eskisehir on June 2 in an attack that was caught by security cameras. He was one of eight people to die in the three weeks of unrest that convulsed the country.