Sunday's 8-2 Barclays Premier League humiliation at Manchester United and the impending closure of the transfer window has prompted a beleaguered Wenger to accelerate his late-summer recruitment drive.

Werder Bremen and Germany defender Mertesacker flew to London today to undergo a medical after being given permission by both club and country.

Arsenal were confident of concluding a deal for the 26-year-old ahead of tomorrow night's transfer deadline, as they were for Brazil left-back Andre Santos, whose move from Fenerbahce was subject today to a medical and personal terms.

The formalities of Park's transfer were all but concluded this afternoon after Wenger gazumped Lille for the signature of the South Korea captain.

Press Association Sport understands Arsenal have ended their interest in Bolton's Gary Cahill, although reports suggest they remain in the market for another defender, even if they sign Mertesacker, as well as a midfielder to replace the departed Cesc Fabregas and Samir Nasri.

A last-gasp spending spree would be music to the ears of disgruntled Gunners fans, who have long urged Wenger to strengthen a squad whose lack of depth has been cruelly exposed of late.

Mertesacker, 26, would provide much-needed height and experience at the back, standing at 6ft 6in and boasting 75 international caps.

Reports suggest the defender, who has previously been linked with Arsenal, could be available for as little as £8million because of Bremen's financial problems.

He is currently on international duty and Germany boss Joachim Low said today: "Per contacted me last night and informed me (about Arsenal's interest).

"I told the player that I would release him for the day."

Arsenal have also agreed a fee with Turkish giants Fenerbahce - reportedly £6.2million - for Santos.

The 28-year-old would help fill the void left by the sales of Gael Clichy to Manchester City and Armand Traore to QPR.

Park, meanwhile, today became an Arsenal player, subject to a formal registration process.

The striker penned what is thought to be an initial two-year contract after it emerged he will be forced to return to his native South Korea in 2013 for a period of military service.

The Gunners signed the 26-year-old from under the noses of Lille, who were convinced they had reached an agreement for the player to join them on Saturday.

Park, who scored 25 goals in 91 Ligue 1 games for Monaco, played at both the 2006 and 2010 World Cups.

He succeed Park Ji-Sung as captain of his country earlier this year following the latter's international retirement.

"I am very honoured and I feel very happy to be at Arsenal," said Park, who will wear the number nine shirt.

"It is a dream to be here and I am really proud to be an Arsenal player. Now I just want to show how good I am and prove myself.

"In my opinion, this is a great club. Now I have to show what I can do on the pitch.

"I will do my best, I will never give up, I will show heart, I will give everything and I hope (the fans) will support me."

Wenger, whose personal intervention reportedly convinced Park to pull out of his move to Lille, added on the club's official website, www.arsenal.com: "We are delighted to have signed Chu.

"He will add true quality to our attacking forces and will be a valuable addition to the squad."

The Gunners have been linked with a host of other names ahead of tomorrow's transfer deadline, including Rennes' Yann M'Vila and Chelsea trio Florent Malouda, Alex and Yossi Benayoun.