DAMASCUS, April 18 (Xinhua) -- The UN security team were "under small arms fire" while conducting a reconnaissance work in Douma east of Damascus, said the Organization for the Prohibition of Chemical Weapons (OPCW) in a statement Wednesday.

In Douma, the security team "came under small arms fire and an explosive was detonated. The reconnaissance team returned to Damascus," according to a statement released by the OPCW.

The OPCW inspectors arrived in Damascus last Saturday to look into allegations of the use of chemical weapons by the Syrian army during the battles in Douma ahead of its liberation from the rebels.

The team held meetings with Syrian government officials, who expressed the government's willingness to cooperate with the mission.

Earlier in the day, Syria's Foreign Ministry said that a security team of the OPCW entered Douma a day earlier to assess the security situation ahead of the entry of the chemical weapon experts.

The ministry said the entry of the security team came upon the request of the OPCW investigators, without mentioning the security incident.

A day earlier, state media outlets in Syria said the experts of the OPCW entered Douma, but the ministry's statement apparently came to clarify that only a security detail of the team entered to assess the situation ahead of the entry of the investigators.

The arrival of the OPCW team comes as the United States and its Western allies have already struck Syrian military positions over the allegations of the toxic gas attack in Douma on April 7.

Western powers have preceded the mission of the OPCW with a series of missile strikes, which U.S. President Donald Trump described as targeting the chemical weapons capabilities of the Syrian regime.

While completely denying the accusations, the Syrian government stressed that it would cooperate and facilitate the work of the OPCW team to expose the reality in Douma, which has become back under the government's control after last week's rebel evacuation to rebel-held areas in northern Syria.

Meanwhile, the OPCW said in its statement Wednesday that the UN security team will continue to work with the Syrian authorities and the Russian military police to review the security situation.

It, however, said that the time of the entry of the investigators to Douma is not known yet due to the security situation in the wake of the security incident.

Both Russian military police and Syrian law enforcement forces entered Douma after the withdrawal of the Islam Army but not all the rebels have withdrawn from Douma as those who stayed agreed to enlist in a police force supervised by the Russians.