Junior oiler Lekoil Limited (LON:LEK) was the major story on AIM this week with its value dropping by around two-thirds after falling victim to con artists posing as the Qatar Investment Authority (QIA).

Shares in the firm were suspended on Monday after the ‘actual’ QIA contacted Lekoil to question the validity of a £138mln (US$184mln) loan supposedly agreed to finance the firm’s drilling activities on the Ogo field in Nigeria.

Lekoil then issued a statement saying the deal had in fact been made with individuals posing as the QIA in a “complex façade” that had involved the company paying the scammers £460,000 (US$600,000) in supposed legal and arrangement fees.

While Lekoil said its losses would be limited to this initial sum, the shares quickly plunged following its return to AIM on Tuesday and at the end of the week were down 66% at 3.2p.

Turning to the wider market, the AIM All-Share was up 1% at 971 during the week, while the FTSE 100 was 0.7% higher at 7,638.

Digital media firm GlobalData PLC (LON:DATA) was hit when Sally Johnson, deputy finance chief of Pearson, said she would be staying on at the publishing giant to replace outgoing CFO Coram Williams. This sent the stock down 10% to 1,265p.

Johnson was due to become the CFO of GlobalData in the first quarter of this year.

Clothing retailer Quiz PLC (LON:QUIZ) saw little Christmas cheer as its sales over the festive period fell short of expectations.

Revenues in the seven weeks to 4 January slumped 9.3% with footfall in UK stores and concessions down by 7%. The shares followed suit over the week and sank 22% to 15p.

It was a similar story for toymaker Character Group PLC (LON:CCT), which fell 19% to 330p as “challenging” Christmas trading hit sales and resulted in profit forecasts falling below market expectations.

A profit warning piled the pressure on hydraulics and pneumatic components maker Flowtech Fluidpower PLC (LON:FLO), which tumbled 18% to 104p. Its earnings are forecast to be around £1.9mln lower than last year after a tough fourth quarter.

Agronomics Limited (LON:ANIC) suffered blowback from investors, sliding 12% to 9p following a 28% decline in the investment firm’s net asset value.

Shares in biotech firm Tiziana Life Sciences PLC (LON:TILS) slumped 17% to 42p after it revealed plans to delist from the AIM market.

Among the risers, a deal with a Japanese rail operator sent shares in AI analytics firm Maestrano Group PLC (LON:MNO) up 18% to 2.7p in the week.

The deal with Nagoya Railroad will use the Corridor.ai platform to detect defects in overhead powerlines, gantries and signals on a section of rail track for two months.

Acquisition news boosted pharma group Ergomed PLC (LON:ERGO), which surged 9% to 427p after acquiring US drug safety firm Ashfield Pharmacovigilance from UDG Healthcare PLC (LON:UDG) for £7.7mln (US$10mln).

Ashfield will add more than 40 new clients to Ergomed’s roster as well as an order book worth £7.5mln (US$9.8mln).

Waste-to-energy group EQTEC PLC (LON:EQT) was lifted 8% to 0.17p after fuel derived from its demonstration plant in France was approved for testing by LERMAB, the University of Lorraine’s research laboratory on wood material.

Data solutions firm D4t4 Solutions PLC (LON:D4T4) also edged up 3% to 211p on the back of several contract wins resulting from its “significant pipeline of new business”.

Daily Mash owner Digitalbox PLC (LON:DBOX) bounced 6% to 7p after it upgraded its profit guidance for the year thanks to a surge in viewership across its websites.

Miner IronRidge Resources Limited (LON:IRR) jumped 12% to 12p after reporting “exceptional” drilling results from its Zaranou gold project in Côte d’Ivoire.

Finally, a profit upgrade drove shares in Diaceutics PLC (LON:DXRX) 15% higher to 117p, with the precision medicine group saying its 2019 earnings will now be ahead of market expectations after a strong finish to the year.