Resource stocks were making advancing strongly on the FTSE 250 on Friday as the sector rebounded after a turbulent week owing to the wider market volatility.Oil explorer Afren led the risers with a gain of nearly 9.0% as West Texas crude oil prices rose to a nine-month high of $98.02 a barrel (up 1.4% on the day) on the back of increasing tensions in the Middle East. Heritage Oil however was lower after being defeated by FTSE 100 group Tullow Oil in a contract dispute taken to the UK High Court. The dispute related to which of the two companies was liable for a tax payment to the Ugandan government.Elsewhere, mining stocks were in demand after Citigroup upgraded the basic resources sector to 'overweight', saying that the category "looks cheap". New World Resources and Ferrexpo were among the better performers.Water group Pennon was pulling back after a strong rise the day before as it benefitted from rumours that the company could be attracting interest from investors in Abu Dhabi.Real estate group Great Portland Estates was performing well after UBS upgraded its rating for the stock from 'neutral' to 'buy', saying that the recent pull-back in the share price has created an opportunity to build positions.Sector peer UNITE, the student accommodation firm, was also a high riser after yesterday placing 16m shares to raise £51.2m to invest into "select regional locations over the next couple of years". The stock was given an extra lift today by Espirito Santo which boosted its target price from 371p to 381p.FTSE 250 - RisersAfren (AFR) 129.30p +8.66%Imagination Technologies Group (IMG) 312.90p +7.42%New World Resources A Shares (NWR) 91.95p +6.30%Lonmin (LMI) 287.90p +5.73%African Barrick Gold (ABG) 135.00p +5.55%Unite Group (UTG) 353.10p +5.37%Ferrexpo (FXPO) 154.00p +5.19%Mondi (MNDI) 815.00p +4.82%NMC Health (NMC) 326.70p +4.71%Pace (PIC) 245.00p +4.66%FTSE 250 - FallersOcado Group (OCDO) 304.70p -5.55%FirstGroup (FGP) 94.40p -3.92%Heritage Oil (HOIL) 138.50p -2.60%Senior (SNR) 252.90p -1.98%Computacenter (CCC) 441.40p -1.89%Salamander Energy (SMDR) 161.50p -1.82%Playtech (PTEC) 647.50p -1.15%Pennon Group (PNN) 663.50p -0.97%Fenner (FENR) 335.90p -0.91%Essar Energy (ESSR) 127.90p -0.85%