The messaging app company has raised $340m from backers including Alphabet and is seeking a valuation higher than the $2.8bn at which it last secured funding.

Slack Technologies, the US-based messaging app developer backed by internet technology group Alphabet, is looking to raise another $150m, the Wall Street Journal reported on Tuesday.

The company is in the process of approaching prospective investors and is seeking a higher valuation than the $2.8bn valuation at which it raised $160m in April 2015, a person familiar with the matter told the WSJ.

Slack started out as a game developer called Tiny Speck in 2009 before pivoting to concentrate…