Rescuers work beside the bodies of victims at the air crash site of a Boeing 737 Ukrainian passenger plane in Parand district, southern Tehran, Iran, on Jan. 8, 2020. (Photo by Ahmad Halabisaz/Xinhua)

Iran's government on Monday denied a "coverup" after it took days for the armed forces to admit a Ukrainian airliner was shot down by mistake last week.

The comments came after a second night of demonstrations in Tehran against the authorities over the disaster.

The Ukraine International Airlines Boeing 737 was shot down shortly after it took off from Tehran before dawn on Wednesday, killing all 176 passengers and crew on board.

The Kiev-bound airliner was brought down hours after Iran had launched a wave of missiles at US troops stationed at Iraqi bases in retaliation for the killing of a top Iranian general. The Islamic republic initially denied Western claims based on US intelligence that the passenger plane had been struck by a missile before admitting it on Saturday.

"In these sorrowful days, many criticisms were directed at relevant officials and authorities," said government spokesman Ali Rabiei.

"Some officials were even accused of lying and a coverup but, in all honesty, that was not the case.

"Lying is intentionally and knowingly faking the truth. Lying is covering up. Lying is knowing a fact and not expressing it or twisting the truth."

Rabiei said all details provided by officials prior to Saturday's admission had been based on the information available to them at the time.

The majority of the people on Flight PS752 were Iranians and Canadians, including dual nationals, and other victims were Ukrainians, Afghans and Britons.

There were seven Swedish citizens as well as 10 people who resided in the EU member country.

China was saddened by the tragedy, and expressed deep condolences to the victims and extended heartfelt sympathies to their families, said Chinese Foreign Ministry spokesperson Geng Shuang at a daily briefing on Monday.

"We have noticed that relevant parties have maintained communication on this matter, and hope that this incident can be properly handled to avoid further complicating the situation," Geng said.

The five nations whose citizens died in the incident will meet in London on Thursday to discuss possible legal action, Ukraine's foreign minister said.

Speaking at the sidelines of an official visit to Singapore on Monday, Vadym Prystaiko said the countries would also discuss compensation and the investigation into the incident. 

Prystaiko said suggestions from Iran that the plane was downed as it flew near a sensitive military base during a time of heightened tensions were "nonsense." He said Tehran had agreed to hand over the plane's black boxes to Kiev for investigation.