Prime Minister Prayuth orders probe into several small explosions in the Thai capital that left two women injured.

Four people have been wounded after at least six small bombs went off in Bangkok, rattling the Thai capital as it hosted a regional summit attended by top diplomats.

Friday’s first explosions were heard during rush hour, just before 9am at two sites near central Bangkok. A third blast was heard shortly afterwards at a government complex hosting several ministries on the northern side of the city. Police recovered at least six bombs exploded at three locations, with one unexploded device also recovered.

Four people were wounded, the Erawan Medical Center said. It added that “none are serious and all are receiving medical attention at hospitals.”

Three of those hurt were women cleaning the street when a bomb went off. Pictures on local websites showed them looking dazed and getting treament from medics. One was seen being loaded into an ambulance.

Thai Prime Minister Prayuth Chan-o-cha has already ordered an investigation into the several small explosions on Friday.

Bangkok is currently hosting a regional security meeting of foreign ministers from the Association of Southeast Asian Nations (ASEAN) and their counterparts from world powers including the United States, China and Russia.

None of the Friday blasts were very close to the meeting venue.

A day earlier, Thai police said they had found two fake bombs near the site hosting the regional security meeting.

The packages prompted a brief security scare on Thursday but were quickly deemed harmless. It was unclear whether the meeting was the target.

Police said two men had been arrested in connection with the fake bombs.

China’s top diplomat Wang Yi and US Secretary of State Mike Pompeo attended the forum along with other regional and global officials.