A man allegedly tried to buy two hand grenades and Semtex explosive from an undercover FBI agent on the dark web, a court has heard.

Mohammed Humza, 29, of Watford, is accused of approaching the agent, who was posing as a seller on dark web trading site AlphaBay, in summer 2016.

The Old Bailey heard that Mr Humza is said to be the person behind the username mh.nn243.

The site, which has since been closed down, was popular for trading illegal items including drugs, firearms and other weapons.

Mr Humza is said to have downloaded a Tor browser – designed to hide the location of the user from surveillance by law enforcement agencies – to his laptop.

In a message to the agent in July 2016, mh.nn243 asked the agent: “What’s the best price you can do for 2 grenades with postage to the UK?”

The user haggled the agent down from 125 US dollars each to 115 US dollars by offering to buy four grenades, before discussing how payment would be made.

In the exchange, the pair discussed the price of delivery to “Watford” and “Hertfordshire”.

The user offered to “finalise early” on one of the grenades, meaning full payment would be made ahead of receipt, while the funds for the second would be placed in escrow under the control of a third party.

The remaining two grenades were to be purchased at the end of the week.

The court heard that after this conversation, the user said to be Humza went quiet and the deal was not completed, but he approached the officer again in early August.

He said he had been away for a while and using someone else’s laptop but asked to “do 1 custom now” on a fragmentation grenade.

The pair eventually agreed a deal for two grenades and mh.nn243 placed cryptocurrency funds into escrow at 9.03pm on August 6.

Prosecutor Benjamin Holt said: “This is not just idle chat – mh.nn243 has actually made payment for the two grenades.”

The court heard the grenades were to be sent to Mr Humza’s address in Fuller Road, Watford, but under his neighbour’s name.

Mr Holt said: “It is not a great disguise, I accept, but it is, we say, the user getting the product delivered to his home address, albeit with his neighbour’s name on the package.”

After being told by the agent that he was out of stock of grenades and having his cryptocurrency refunded, the user attempted to buy Semtex and a fuse detonator.

Mr Humza, who is not present at trial, previously denied attempting to possess explosive substances for unlawful purposes between July 14 and September 5 2016.

It is not in dispute that the dark web deals took place, but Humza has said he is not the person in control of the mh.nn243 user name.

The jury was told that Humza’s email address is mh.nn40@gmail.com – made up of his and his wife’s initials.

The numbers 24 and 3 are said to have come from his postcode and door number respectively, and feature in a number of his online usernames, including for his internet banking apps.

An unsent text message on his mobile phone read “mh.nn243/ALPHABAY/HUMZA816198” – the numeric sequence 816198was part of mh.nn243’s AlphaBay account password.

The trial is expected to last two to three days.

The judge, Mrs Justice McGowan, told the jury: “Mr Humza has chosen not to attend his trial. That does not mean he is guilty, it simply means he has chosen not to attend the trial.

“It does not prove and is not part of proving he committed this offence.”