ISDN Holdings, one of six companies that were queried by the Singapore Exchange last week over unusual trading activity, has clarified that it is not linked to the other five firms.

The company said in a statement on Monday morning that it "has no connection, directly or indirectly, with the entities".

This follows a Straits Times report on Monday that had indicated the firm was connected to companies including Blumont Group, Asiasons Capital and Liongold Corp. The latter three firms were suspended from trading on Friday but had their trading halts lifted on Sunday.

ISDN was queried last Friday over a "substantial" decrease in its share price but had responded that it was not aware of any possible explanation for the price drop or trading activity.