CAIRO: An Egyptian opposition group accused the government on Wednesday of covering up torture at the hands of security forces.

The charge came after a government forensic report claimed 28-year-old activist Mohammed el-Gindy was killed in a car accident. It contradicted family and friends, who said he died after he was electrocuted and beaten on his head repeatedly in detention earlier this month.

In a separate case, activists also accused authorities of trying to conceal the identity and age of 12-year-old Omar Salah, killed by security forces' gunfire during clashes around Cairo's Tahrir Square on Feb. 3.

In El-Gindy's death, initially the justice minister, who oversees the state forensic authority, said it was caused by a car accident. But then the chief of the forensic authority denied the justice minister's statement and said the report was not final.

When the final report came out, it listed car accident as the cause of death, leading some to suspect foul play. Security officials deny that they held him.

El-Gindy was a member of the Popular Current opposition group, which called the forensic report "fraudulent" and said it will challenge it.

"The Popular Current plans to pursue a legal complaint, charging that the forensic authorities have forged it, and will go after all those who took part in this crime," the statement said.

It said those people including President Mohammed Morsi and his interior and justice minister.

The group said it has its own medical reports prepared by doctors who saw el-Gindy in the hospital and morgue. It shows that el-Gindy was strangled, electrocuted on his tongue, and had a deep gash in the back of his neck. They claimed he was tortured during detention.

El-Gindy, who had taken part in anti-government protests that began last month, died Feb. 4. Word of his death provoked violent protests in his hometown of Tanta northwest of Cairo.

In the case of the child killed, security officials had said they mistakenly killed a street vendor on Feb. 3. Security officials did not report that the dead person was a 12-year-old and didn't record the case in hospital records or allow a forensic report, according to activists who compile data from visits to hospitals, morgues and police stations.

Security officials had no comments about Salah's case. Attempts to reach the spokesman for the Interior Ministry were unsuccessful.

The two deaths came during a heavy-handed crackdown by security forces on protesters that had the opposition charging police had returned to the repressive tactics used under the ousted regime of autocrat Hosni Mubarak.

Nearly 70 civilians were killed in the wave of clashes that began around the second anniversary of Egypt's uprising on Jan. 25. Violence has been tapering off but there are still sporadic clashes.

Nazly Hussein, an activist who has been recording cases of detained and injured during protests, said nearly 400 protesters were detained in Cairo. She alleged many of them were held first in security camps without proper procedures and tortured before being transferred to jails and prosecutors for questioning.

Of those, more than 100 were children under the age of 18 and 42 of those were under 15, said Ghada Shahbander, a rights activist. Egyptian law prohibits detention of children under age 15.

The list of those detained or currently facing charges is patchy because activists and lawyers are still working to compile lists and struggling with a lack of due process.

Many of the detained have been released but at least one activist is still believed to be missing.

"There is no transparency in any of the information we are getting," said Hussein. "We coincidentally found out about (the 12-year old) Omar Salah. ... We don't know what else may be happening."

Opposition activists charge that police, the main target of discontent in the uprising that forced Mubarak out, continue to enjoy impunity for past human rights violations. As a result, they say, violations continue.

The dispute surrounding El-Gindy's death was reminiscent of the case of Khaled Said - one of the sparks of the uprising.

Said died in 2010 of police abuse but authorities tried to claim he suffocated on a stash of drugs.

The case sparked an unprecedented nationwide protest movement.